The Milan keeper could have done more about the second goal, however, as he flapped at a cross, allowing Borja Valero to tuck away the rebound and seal all three points for his side.
You can read how a frustrating and miserable night for Milan unfolded with Sports Mole's live minute-by-minute coverage below.
7.15pmGood evening! Thank you very much for joining Sports Mole for tonight's Serie A clash between two sides who will be eager to prove a point as AC Milan host Fiorentina at the San Siro.
7.17pmWe'll start by looking at our hosts tonight, and it would be fair to say that Milan have not exactly made an ideal start to their season. One of Italian football's true giants currently sit mid-table after 10 games, and perhaps the most damning indictment on them is that it is a deserved position.
7.19pmMilan have really struggled for any sort of consistency this season, winning three, drawing three and losing four of their 10 matches so far. We are not even a third of the way through the season but already they are a long way out of the title race - although that can also be put down to Roma's relentless pursuit of perfection. More worryingly for the Rossoneri, they are in danger of falling too far behind the top three, meaning that they would miss out on a spot in next year's Champions League - a tournament they are so synonymous with.
7.21pmA select group of teams, namely Roma, Napoli and Juventus, have really raised the bar this season and Milan simply haven't been able to keep up. They are already 13 points off third place and it would take an almighty comeback for them to finish in the top three this season.
7.23pmIf they are to pull off such a comeback, they must sort out a number of issues, with the number one priority being their leaky defence. Milan have been plagued by injuries so far this season, but even that isn't a good enough excuse for some of their defensive showings. They have conceded more goals (17) than any other team in the top half and are particularly susceptible to set pieces.
7.25pmWith such poor defensive statistics, it isn't surprising that Milan have struggled to pick up wins on a regular basis this season. They have only won one of their last six matches in all competitions, although they have had a tough run of fixtures against the likes of Juventus, Barcelona and Lazio.
7.27pmDespite this, their home form is actually quite good this season. They have only been beaten once at the San Siro this season - against second-placed Napoli - and are unbeaten in their last four games in front of their own fans.
7.29pmThose four games yielded two wins and two draws, although the Rossoneri failed to score more than one goal in any of those games. Scoring goals hasn't been their biggest problem so far this season - as shown by the fact that no-one outside the top six has scored more in Serie A - but they do still need to improve up front if they are to launch an unlikely bid for a top three spot.
7.31pmFiorentina will also have an eye on a top three spot, and they are certainly better placed than their opponents today to get one. They currently sit sixth in the table after a good run of form that was halted by Napoli on Wednesday. Fiorentina played very well in that match despite losing, so they should still come into today's game with plenty of confidence.
7.33pmThat defeat was Fiorentina's only one in their last seven matches in all competitions, but things aren't so rosy for the Viola in the league. They have only won two of their last six Serie A games, leaving then seven points off the top three but still six clear of Milan.
7.33pmAway from home they are in fine form, as just one defeat in their seven away matches this season is testament to. That sole loss came in this stadium, however, as Inter triumphed 2-1. Other than that, however, Fiorentina have won five and drawn won of their other six games on their travels so far this season.
7.35pmTEAM NEWS: Time for some team news from both sides, and Milan's side is notable for the absence of Robinho, who just makes the bench. Balotelli starts up front for the hosts, while Gabriel continues in goal after Abbiati was once again deemed not fit enough to start. Fiorentina drop Joaquin to the bench but unsurprisingly keep the league's top scorer Giuseppe Rossi in their side. Full team news for both sides on the way.
7.37pmAC MILAN STARTING XI: Gabriel; Zaccardo, Zapata, Abate; Constant, Kaka, Muntari, Birsa, De Jong, Montolivo; Balotelli
7.41pmThe dangermen for both sides are to be found, as usual, up front. For the hosts, Balotelli can be the key to them playing well or playing badly. The enigmatic Italian was poor in his last outing but is the type of player who can win a game from nothing with a moment of magic. Fiorentina, meanwhile, have Rossi, who has made a remarkable recovery from his serious knee injury and now leads the league in goals with nine. He will fancy his chances of adding to that tally against such a shaky defence tonight.
7.43pmPREDICTION: This one is a tough one to call today, but I think AC Milan's recent bad form and Fiorentina's decent away record could conspire to create a draw. I'll go for 2-2.
1 minKICKOFF: AC Milan get us underway at the San Siro as they look to put such a disappointing start to the season behind them. They approach every game as one with the potential to kick-start their season at the moment, and today will be no exception.
3 minThis could be an emotional match for Ambrosini, who returns to the San Siro having spent so long here as a Milan player. He was given a tremendous reception from the home fans, who remember fondly his role in the glory days of the club even if he was never the star player amongst the likes of Kaka, Shevchenko and Maldini.
5 minMilan have made a bright start to this match as they look to take an early lead. No threat to the opposition goal, however, as Muntari's long-range strike is blocked behind for a corner.
7 minMuntari goes for goal from range again, and once more it is never struggling the keeper. It does reach the goal without the aid of a deflection this time, but the keeper is happy to watch it sail a few yards wide of his post.
9 minMilan are looking good enough on the ball at the moment, but they are defending very deep when Fiorentina have it. They aren't putting any pressure on the likes of Ambrosini in midfield, despite having made the brighter start to the match. They shouldn't really be letting the visitors settle into this game so easily.
11 minBalotelli shimmies away from one man with a drop of the shoulder and then lines up Ambrosini with a few step-overs, but the former Milan midfielder puts in a heavy challenge on the left side of the box. He got plenty of the ball, but too much of the player for the referee's liking and he awards a free kick.
12 minBalotelli takes the free kick duties upon himself, but his delivery is disappointing as it is cleared by the first man. You could see what he was trying to do, whipping it in towards the far post, but he didn't get enough height on it.
14 minSuperb play from Ryder as he races past Zaccardo and keeps the ball in before cutting inside and looking for a teammate in the middle. In the end, his cross is too close to Gabriel, but it was good play from the Brazilian, and electrifying pace.
16 minCHANCE! Milan have had a few corners from the left in the opening quarter of an hour, and this latest one provides their best chance of the match so far. Zapata times his run to the front post perfectly and connects with a powerful header, but he can't keep it down. He probably should have at least hit the target there.
18 minBalotelli goes for goal from around 40 yards out, wasting a good attacking platform with a wayward shot that goes high and wide. He doesn't look like he is having one of his better days so far this evening.
20 minUPDATE: There is one other match also going on in Serie A at the moment, and Napoli have taken the lead in it. Callejon has given Rafael Benitez's side a 1-0 lead against Catania.
21 minSAVE! Another decent opening for Milan as Kaka makes headway down the left flank before rolling the ball across the edge of the box for Muntari. He doesn't quite catch his shot, however, and his rather tame effort is gathered by Neto.
23 minMilan have probably just about had the best of these opening stages, but we're still waiting for our first real chance. Zapata and Muntari have both had decent openings, but neither side has really looked like scoring so far.
24 minUPDATE: Napoli have doubled their lead against Catania, with Hamsik making it 2-0 to Benitez's side.
26 minFiorentina will take some heart from the fact that it is almost three years since they were beaten by Milan here. The corresponding match last season finished 3-1 to the Viola, while Milan's last win came in November 2010, with Zlatan Ibrahimovic getting the only goal of the game. What would they give to have a player like him now?
27 minGOAL! AC Milan 0-1 Fiorentina (Juan Manuel Vargas)
27 minFiorentina break the deadlock just before the half-hour mark through a Vargas free kick. It is poor on Milan's part as their wall simply doesn't do the job, with Vargas's low strike deflecting off Muntari's shins and past a helpless Gabriel.
29 minYELLOW CARD! Ryder Matos becomes the first player in the book after a little scuffle with his compatriot Kaka. He is all smiles moments later, however, as the handbags are swiftly forgotten about.
31 minThings look rather worrying for Milan right now. Another defeat, especially one at home, would really leave their season in tatters. It could also be the final straw for Allegri, who is already under heavy pressure for their poor start to the season. You can sense that the crowd is getting restless now too, which is just what they don't need.
32 minRossi is brought down through a combination of Kaka and De Jong, and Fiorentina have another free kick in a good position here. This one is slightly further out than the last, but with Milan's poor showing in the wall last time anything could happen here.
33 minValero chooses not to shoot, but instead hangs a cross towards the far post that Gabriel comfortably collects.
34 minFIORENTINA SUB: That is sad for Ambrosini as he is forced off in a match that has such strong emotional attachments for him. He gets a standing ovation from the entire crowd as he walks off to be replaced by Matias Vecino.
36 minGreat pressure from Valero as he sprints almost the length of the field to hound Gabriel in possession, forcing the keeper to concede a corner. Superb desire from the visitors.
38 minFiorentina are looking comfortable at the moment, and Milan are still really struggling to create anything in the final third. This must be so frustrating for everyone connected with such a great club.
40 minBalotelli in particular has been very disappointing so far today. There are rumours that he isn't happy in Milan at the moment, and he is certainly playing as if that is the case.
42 minAs if to emphasise that point, he goes down in a heap inside the box after minimal contact with a defender. He stays down for a while too, but he will be able to continue here as it wasn't exactly a crunching challenge that felled him there.
44 minMilan just look woefully ineffective at the moment. They don't appear to have the cutting edge that will get them through this Fiorentina defence. The visitors haven't been much better, to be honest, but the onus is on Milan as they are at home and currently trail.
45 minThere will be two minutes of added time at the end of this half.
45+1 minPENALTY SHOUT! Balotelli once again goes down in the box, this time under the challenge of Pasqual. Both sets of players are incensed as Milan want a spot kick and Fiorentina want a card. There was contact, but Balotelli looked for it and left his leg out in an attempt to con the ref, but it didn't work.
8.38pmYet another half of frustration comes to an end for Milan, who trail Fiorentina 1-0 at the break. It has not been a classic match by any stretch of the imagination, with limited chances for either side.
8.40pmThe visitors' goal did have an element of luck about it as Vargas's low free kick deflected off the wall and past Gabriel. However, the lucky deflection had its roots in poor play from Milan as their wall allowed gaps to appear. The simple fact is that if the wall did their job, this match would still be goalless.
8.42pmMilan did start brighter than their opponents today, and had what is probably the clearest chance of the match when Zapata ran to the near post to connect with a Kaka corner, only to send his header over the bar. Other than that, a weak Muntari strike from the edge of the box is all they have to speak of so far, which is simply not enough at home for a team like Milan.
8.44pmFiorentina haven't exactly besieged the Milan goal either, however. Vargas's goal is the only time they have remotely looked like scoring, and even that wasn't the best strike and needed a deflection to help it on its way.
8.46pmOverall, not much to shout about for either side, then. The performance may almost be secondary for Milan right now, however. The number one priority for them is to start picking up points, and only then should they start focusing on actually playing well. It remains to be seen how long the patience of the fans holds out though, as there are signs of them becoming increasingly frustrated already.
8.48pmBalotelli's tumble before half time could be his last action in this match. The ineffective striker limped off the field a little earlier than his teammates, and Matri was warming up on the sideline at the time too. I would be surprised to see the former Man City striker return and, in truth, that could be a good thing for Milan as he has been poor so far today.
8.50pmIn fact, Balotelli has come out for the second half with his teammates, so he will continue in this match. He will be hoping for a better performance in this second half than he managed in the first.
46 minKICKOFF: We're back underway at the San Siro as Milan look to turn this match around. Can they find an equaliser and then a winner in the remaining 45 minutes, or will Fiorentina hold out?
47 minBalotelli brings the ball down in the area with a nice touch before laying the ball off to Birsa, whose shot is deflected behind for a corner. That is better from the hosts.
49 minConstant takes a blow to the head after competing for the ball with Rossi on the edge of the Fiorentina box. The referee opts for a drop-ball rather than giving Milan a free kick in a good position.
50 minYELLOW CARD! Alberto Aquilani goes into the book for a heavy challenge in midfield. He can have no complaints about that one.
52 minVecino has space to run into down the left, but instead of pinning his ears back and running towards goal, he just holds back and tries to clip a cross-field pass towards Rossi with the outside of his boot. His pass flies straight into the arms of the keeper, however, which is a waste of a good chance for the visitors.
54 minFiorentina are getting increasingly upset with what they perceive as simulation from the Milan players. No doubt their grievances lie in the fact that Cuadrado was shown a very harsh red card for a supposed dive in their last outing.
56 minAquilani is walking on thin ice here as he commits another cynical foul that draws remonstrations from the Milan players. They want the midfielder to be shown a second yellow, but the referee makes the right decision in merely giving him a warning.
57 minAC MILAN SUB: Birsa's afternoon is over as he makes his way off the field to be replaced by young Mbaye Niang.
58 minNiang instantly increases the volume in the stadium by challenging Neto for the ball. The Fiorentina keeper isn't happy with it and has plenty to say to Niang, causing Balotelli to step in and take issue with the keeper. A rare moment of passion from the striker this evening!
60 minA reminder that, as things stand right now, Fiorentina will be back in the top four with these three points. They will stay there until at least tomorrow, while Milan could also be in the bottom half tomorrow.
61 minYELLOW CARD! More needlessly stupid play from Balotelli as he charges into the back of Neto while the keeper was shepherding the ball back. He picks up a card for his silly play, and he takes it with a wry smile.
63 minAllegri must be thinking about taking Balotelli off now. He is one silly foul away from being sent off now and he hasn't not had an impact on the game at all. I have seen the Italian striker have some ineffective games in his topsy-turvy career so far, but this may be one of the worst yet.
65 minMilan have shown glimpses of being able to threaten in this second half, but they are yet to create a really good chance - in this half or the last. It could be time to bring Robinho on soon, as at least he would provide something a little different. They need something to spark them into action.
67 minIf the hosts are going to get anything out of this match, it looks most likely to come from their left flank. They are experiencing a little joy there now, with Constant and Muntari finding space to put crosses into the box.
69 minMILAN SUB: Riccardo Saponara hasn't had much game time so far this season - just two minutes to be precise - but he gets the nod ahead of Matri and Robinho as Milan look to turn this game around. Off comes Muntari.
71 minAgain Milan attack down the left and Saponara is almost played in to make an immediate impact. The pass is just intercepted, however, as Fiorentina put it behind for a corner which comes to nothing.
73 minGOAL! AC Milan 0-2 Fiorentina (Borja Valero)
73 minThings just go from bad to worse for Milan. Joaquin, with his first action, beats Saponara down the right and sends a dangerous cross into the area that Gabriel tries to claim. He only flaps at it, however, and the ball falls to the feet of Valero, who lashes it into the roof of the net.
75 minAbate has a decent chance to haul his side right back into the game immediately after going two behind, but he can't keep his shot down. They need to do better in such circumstances.
77 minThere is still time for Milan to get themselves back into this game, but something needs to change if that is to happen. They haven't really looked like scoring at all in this match, and it is tough to see where any late comeback will come from.
79 minI am very surprised that we haven't seen Robinho or Matri in this match so far. Something needs to give Milan a spark and, for all Balotelli's ability to come up with something special out of the blue, he has not been able to do anything today and should have been withdrawn a while ago.
81 minThis is a big 10 minutes for Milan and Allegri. The under-fire boss could do worse than to go all out attack right now, as his job is becoming increasingly under threat with every passing poor result.
83 minThings only get harder for Milan too. Their next match is against Barcelona at the Camp Nou - a fixture that the best sides in the world would struggle with. This Milan is certainly not one of the best sides in the world, and if they play like this in midweek it could be an embarrassment for the Italian side.
85 minStill no chances to report from either side in the last few minutes. There has been very little goalmouth action today, but Fiorentina have made the most of their rare visits to the opposition final third.
87 minVecino goes for goal from around 25 yards out, but his curling effort goes a few yards wide and is never really troubling Gabriel. Still, the ball is at the right end of the field as far as Fiorentina are concerned.
89 minIt is Fiorentina who are controlling the ball late on here, and Milan seem to have accepted their fate of a 2-0 defeat. The visitors have very rarely been troubled today, and even with nothing to lose Milan aren't attacking the Fiorentina defence. Very strange.
90 minFIORENTINA SUB: Ruben Olivera will come on for the closing moments, taking the place of Ryder Matos.
90+1 minThere will be three minutes of added time at the end of this match.
9.41pmThe full-time whistle is greeted by boos and jeers from the home fans as they see their side fall to yet another defeat that will likely take them into the bottom half of the table when the full round of matches is completed tomorrow. Fiorentina, meanwhile, are doing a mini lap of honour after another famous win in the San Siro takes them into the top four.
9.43pmMilan just lacked creativity, urgency and, to be brutally honest, quality today. Fiorentina weren't exactly at their best but they looked comfortable throughout and deserved their win tonight. It may be too early to call this a crisis at Milan, but something certainly needs to change soon.
9.45pmRight, that's all we have time for tonight. Thank you for joining Sports Mole for another miserable night for Milan as they fall to their fifth league defeat of the season. Fiorentina, on the other hand, pick up a third consecutive win over Milan in the San Siro to move up to fourth in the table. I will leave you with our match report, and be sure to check back in with us tomorrow for plenty more live action. Until then, though, it is goodbye from me!