Flamini was shown a straight red card late on as both sides were forced to settle for a point in a hard-fought clash.
Look back at an entertaining clash between second and third in Serie A with Sports Mole's minute-by-minute commentary below.
7.16pmEvening Calcio fans and welcome to Sports Mole's live coverage of without doubt the biggest match in Serie A this weekend. Second faces third at the San Siro tonight as Milan defend their proud unbeaten record in 2013 against Napoli.
7.18pmMilan are under pressure tonight to prove they can deliver without Mario Balotelli leading the line. The talented striker serves the first game of a three-match ban for insulting officials tonight, forcing Massimiliano Allegri to shuffle his pack. The Rossoneri are yet to taste defeat this year in the league but face a severe test against Walter Mazzarri's men this evening.
7.20pmNapoli travel to the San Siro on a run of three successive wins, with Edinson Cavani rediscovering form after a lean patch in March. The forward will be supported by Goran Pandev and Marek Hamsik tonight as the visitors try to wrap up second place and keep their fading title challenge alive.
7.22pmBREAKING TEAM NEWS! There is a real surprise in Milan's starting XI tonight, with Milan coach Allegri deciding to leave out Stephan El Shaarawy. Giampaolo Pazzini is preferred in attack, with Robinho also getting a rare start on the left-hand side. A full look at both lineups in full will follow in just a few moments.
7.24pmMILAN: Abbiati; Abate, Zapata, Mexes, Constant, Flamini, Montolivo, Muntari, Boateng, Pazzini, Robinho
7.26pmNAPOLI: De Sanctis, Campagnaro, Cannavaro, Britos, Maggio, Behrami, Dzemaili, Hamsik, Zuniga, Pandev, Cavani
7.28pmRobinho's inclusion tonight is a genuine surprise. The Brazilian has been a peripheral figure all season but has the chance to remind potential suitors of his qualities from the start tonight. M'Baye Niang was rumoured to be in contention for a start this evening but has to settle for a place on the bench alongside El Shaarawy.
7.30pmKevin Constant get the nod at full-back for Milan, while Sully Muntari comes in for the injured Massimo Ambrosini to partner Mathieu Flamini and Riccardo Montolivo in central midfield. Bojan Krcic is out for the home side tonight after suffering a calf problem in training.
7.32pmNapoli boss Mazzarri has decided to make just once change to the side that beat Genoa last weekend, with Juan Zuniga preferred to Pablo Armero at wing-back. Blerim Dzemaili keeps his place in central midfield ahead of Gokhan Inler after scoring four goals in his last two matches.
7.34pmPandev gets the nod to partner Cavani in attack ahead of Lorenzo Insigne, who has to settle for a place on the bench. Marek Hamsik will take up a familiar advanced position in midfield in support of the front two, with the visitors looking to break to deadly effect on the counter.
7.36pmTonight's clash will go a long way to deciding which side will claim second spot and an automatic place in next season's Champions League. Napoli currently hold a four-point advantage over Milan, who are trying to hold off a late charge from Fiorentina in fourth. Both sides need the win which should make tonight's clash an entertaining one. Fingers crossed!
7.38pmA repeat of this season's earlier clash between the two sides tonight would be most welcome. Their meeting at the San Paolo saw Milan come from two goal to draw 2-2 in a pulsating clash, thanks to a clinical brace from El Shaarawy. The Little Pharaoh has struggled for form and with a persistent knee problem has lost his place this evening. Pazzi, Boateng and Robinho are the men charged with breaking down Napoli's stubborn back three this evening.
7.40pmNapoli have a very poor record at the San Siro and are without an away win against Milan since 1986. In league and cup they gone 19 games without tasting victory at the Giuseppe Meazza, what a chance they have tonight to end that barren run and all but confirm a top-two finish in Serie A.
7.43pmPREDICTION! With the two sides due out shortly at the San Siro there is just time for me to hazard a guess at the scoreline in this massive match. Milan are in form but I think the loss of key players will stop them winning this evening. Both sides are well capable of scoring and I think Napoli will have enough quality in the final third to earn a 2-2 draw, with Pazzini and Dzemaili both to get on the scoresheet.
7.45pmThe two sides head onto the field at a packed San Siro, with an estimated crowd of over 70,000 packed into the stadium tonight. Around 10,000 Napoli supporters are reported to have travelled North for the clash, will they be rewarded with a famous away win tonight?
7.47pmThe pre-match rituals are neatly complete as we spot former Milan striker Andriy Shevchenko in attendance. We are just a few moments from getting this hotly-anticipated clash underway!
2 minNapoli kickoff shooting from right to left and immediately attack through Zuniga, who helps the home side keep possession in the opposition half. Britos quickly sends a stray pass to Montolivo and allows Milan the chance to enjoy their first touches of the night.
4 minRobinho shows a quick turn of pace as he flies inside Dzemaili with a clever touch. The winger is back in the action quickly but this time is unable to control a pass out wide from Constant.
6 minNapoli win the first corner kick but Boateng is on hand to head clear at the far post. The visitors then attack down the right through Maggio, who attempts to shoot rather than pick out a pass inside. His deflected drive is well wide and prevented from going out for a corner kick by an alert dive from Abbiati.
8 minSAVE! De Sanctis is forced to make a late save as a deflected drive from Boateng flies towards his near post. The goalkeeper just about does enough to make the ball scramble beyond the near post, with Napoli eventually recovering to scramble clear Robinho's cross on the follow-up.
10 minMilan enjoy a sustained spell of possession in the final third as Flamini and Abate combine with a clever exchange down the right, winning a corner kick in the process. Zapata meets the delivery unmarked but his powerful header flies well over the far post. Encouraging signs early on here for the home side.
12 minThe visitors calm things down and launch a counter as Maggio finds Dzemaili with a precise pass inside. The midfielder surprisingly decides not to shoot given his recent scoring form, instead choosing to look for Pandev's dart into the penalty area. His pass lacks power and is cleared by an important interception from Mexes.
14 minMontolivo goes down clutching his face after clashing with Pandev in aerial tussle. The referee awards a free kick 35 yards from goal, which Milan take short and work out wide to Boateng. His looping cross into the box lacks power, but Napoli quickly concede possession thanks to a poor pass from Dzemaili. Constant intercepts and crosses to Boateng, who arrives late to shoot wide with low effort. The visitors are yet to switch on defensively but have not been punished so far.
16 minCavani wins a corner at the other end after flicking a long ball forward back of Zapata. Napoli decide to take short in search of Cannavaro, but his cross is aimless and fails to beat the first defender at the near post.
18 minMaggio takes on Constant in a driving run forward, with the Milan defender showing pace and power to shield the ball out for a goal kick. Milan quickly charge forward at the other end through Boateng, but his cross is blocked by Britos and ran clear by Pandev, who wins a free kick after drawing a foul from Montolivo.
20 minHamsik gets involved for the first time tonight, winning a corner kick thanks to a double deflection on his cross from Flamini. Napoli once again fail to cross with purpose from the corner kick as Cannavaro's pass to Pandev catches him offside, allowing Milan the chance to clear their lines.
22 minPandev wants a penalty kick after charging into the box and making contact with Mexes. The Milan defender definitely made contact but also claimed the ball in a well-timed tackle as the referee waves away protests from the visitors.
24 minMontolivo picks out Pazzi with long through ball, but despite a neat first touch Cannavaro is on hand to clear to safety. Cavani has noticeably dropped deeper in the last few minutes, perhaps a sign of frustration at the lack of service he has received so far tonight.
26 minMilan build a concerted attack with possession in the final third and eventually win a corner kick, which Robinho takes short to Montolivo. Zapata is up at the far post to head back across goal, where De Sanctis is out quickly to claim and stop Pazzini making contact at full stretch.
28 minZuniga wins a cheap free kick after being brought down by Boateng, which Napoli take short and work wide to Pandev. His pass inside finds Hamsik, who in turn searches for Cavani with a diagonal pass towards the far post. Unfortunately for Napoli the forward has drifted into an offside position and the chance is gone.
30 minGOAL! Milan 1-0 Napoli (Flamini)
32 minThe deadlock has been broken at the San Siro Flamini gives Milan the lead with his second goal in as many games. He makes an intelligent run beyond Hamsik and is first to pounce on a loose ball from 20 yards. His first-time shot curls away from De Sancits and has enough power to nestle in the bottom corner. Advantage Milan in the race for second place.
34 minGOAL! Milan 1-1 Napoli (Pandev)
36 minQuite incredible scenes at the San Siro as the visitors draw level within two minutes. Hamsik gives Flamini a taste of his own medicine to burst clear in the final third and send an inviting cross into the penalty area. Pandev times his run perfectly to meet the pass and smash home from close range.
38 minA frenetic five minutes continues as Milan burst clear an appeal for a penalty as Britos tangles with Pazzini in the penalty area. The referee waves away protests as Napoli break in numbers at the other end. Milan have an injury problem meanwhile and it looks like Boateng will have to be replaced.
40 minSUBSTITUTION: Boateng is indeed forced off and appears to be clutching his knee in some discomfort as he trudges towards the touchline. Niang is quickly called upon to replace the Ghanaian and immediately takes up an advanced position out wide.
42 minThe end-to-end action continues with Dzemaili spotting the chance to play in Cavani with long forward pass, but once again the forward is marginally offside. Milan stride forward at the other end as Montolivo keeps De Sanctis with a low shoot that the keeper catches with relative ease.
44 minCHANCE! Cavani has come agonisingly close to giving the Napoli the lead with fine effort from close range. The forward showed wonderful close control to bring a long pass under his spell just inside the penalty area. He is forced to take the shot quickly but his looping chip is just tipped wide by Abbiati at full stretch.
45 min+1Milan look to close out one additional minute in attack as Niang finds Robinho after doing brilliantly to rob possession. He drives forward and collects a return pass but can only drive a powerful low strike well past the far post.
8.36pmHALF-TIME Milan 1-1 Napoli
8.38pmA pulsating 45 minutes comes to a close at the San Siro, with Napoli building momentum after recovering quickly to force their way back into the match. Pandev's equaliser came less than three minutes after the opening goal from Flamini, with Milan just showing signs of nerves as the half drew to a close.
8.40pmMilan suffered a huge blow just before the break as Boateng was forced off with a knee injury. With Balotelli suspended and El Shaarawy not fully fit the Rossoneri can ill afford to lose any more key players in the fight for Champions League places.
8.42pmThe home side were excellent in patches during the first period, with midfield runners allowing Milan to swarm forward in numbers. Flamini typified that approach with his goal, driving into the final third before producing an assured finish from just outside the penalty area.
8.44pmAllegri's men have also done well to keep Cavani under wraps for most of the first half, bar a late chance that the forward really should have taken. Zapata and Mexes look steady, with Hamsik only managing to unlock a deep defence on one occasion tonight. Napoli made the most of that break and will now be confident of avoiding defeat to stay clear in second place.
8.46pmThe ownness is definitely on Milan to press the action after the interval if they want to keep their chase of a top-two finish alive. El Shaarawy may not be fully fit and one booking away from a suspension but expect to see him before too long if the scoreline stays level.
8.48pmBoth sides possess attacking options on the bench, with Napoli holding a real wild card in Lorenzo Insigne. The wildly inconsistent forward is capable of producing magic moments on his day and may be pressed into action late on.
8.50pmThe two teams are back out at the San Siro as we prepare to begin a second half that will go a long way to deciding who finishes second in Serie A this season.
47 minBoth managers have decided against changes at half-time as Milan ger the match back underway. El Shaarawy has taken his tracksuit off on the touchline however and will likely be introduced at any moment. Milan begin the second half in attack as Niang crosses in search of Pazzini, but Britos gets to the ball first and heads clear with power.
49 minCavani drops deep and helps Napoli switch play with a whipped pass out wide to Maggio. Eventually Abate wins possession back for the home side and launches clear to Niang, who wins a free kick after being wrestled to the ground by a strong challenge from Behrami.
51 minPandev aims a powerful drive from distance towards goal after finding space just outside the penalty area. His strike arrows towards the far corner but in the end lacks venom and is caught cleanly by Abbiati. Napoli have started the second half strongly and look comfortable in possession.
53 minHamsik does brilliantly to evade a strong tackle from Montolivo but runs into trouble and is stopped by a fine covering challenge from Mexes. El Shaarawy is now patrolling the touchline in his kit but still waits for the thumbs up from Allegri to enter the fray.
55 minFlamini sends a tame low shot into the waiting arms of De Sanctis, much to the disgust of Pazzi who wanted a pass into the penalty area. At the other end Napoli break quickly as Hamsik looks for Cavani with a pass in-behind, but the ball just lacks pace and is scrambled clear by a combination of touches from Zapata and Abbiati.
58 minBoth sides are just struggling to carve out a clear-cut opportunity as the pace notably slows at the San Siro. Flamini is again racing forward but has to settle for a corner kick after Behrami's important late interception. Robinho's delivery from the corner is an absolute shocker, with the Milan faithful letting the Brazilian know how they feel with audible disappointment.
60 minNapoli concede a free kick as Maggio raises a high boot in a challenge with Constant. The visitors quickly clear and counter through Hamsik, who is stopped from finding Pandev unmarked inside by a superb tackle from Abate, who shows persistence to win the ball importantly for Milan.
62 minMilan have a set piece just outside the penalty area after Behrami caught Montolivo with a late tackle. He wants to take the free kick but Niang is also desperate to shoot at goal. The Frenchman takes and wastes the chance with a wayward drive that flies harmlessly over the far corner.
64 minThe visitors look happy to defend from their own penalty area and look to hit Cavani on the counter. Milan are being challenged to break the home side down as Abate creates an overlap down the right, but his powerful cross flies out for a goal kick after missing a packed penalty area.
66 minYELLOW CARD! De Sanctis picks up a silly caution for time wasting after taking to long with a goal kick. A vocal home support behind the goal definitely had a part to play in that caution, which triggers a one-match ban for the experienced goalkeeper.
68 minSUBSTITUTION: After teasing us with the arrival of El Shaarawy it is actually Napoli who make the attacking change. The goalscorer Pandev has been withdrawn for Insigne, who races straight into an advanced position alongside Cavani.
70 minSUBSTITUTION: A second change in as many minutes for Napoli, who make a slightly surprising change as Hamsik comes off for Armero. Mazzarri goes more conservative to introduce a more defensive option, perhaps a sign that he is happy with a point this evening.
72 minRED CARD! Flamini has received a straight red card for a shocking late tackle on Zuniga. His sliding challenge saw him raise both feet and fly in with studs up, leaving the referee with little choice but to send the Frenchman off. A melee breaks out following the incident, with Maggio booked for his angry protest to the referee.
74 minSUBSTITUTION: Milan finally bring on El Shaarawy as Robinho makes way for the little pharaoh. His remit will now be to provide fresh legs in attack with the home side at a man disadvantage. Zuniga is thankfully back on his feet after bearing the brunt of Flamini's tackle and looks fine to continue.
76 minYELLOW CARD! Cavani picks up his ninth yellow card of the season for a forceful late lunge and must now be careful in the last 15 minutes as the match begins to turn nasty in the closing stages.
78 minNapoli use their extra man to keep possession for a prolonged spell before Maggio ends the passing move after being tackled by Constant. Milan look slightly subdued in the closing stages as they struggle to win the ball back from Insigne, who finds Cavani in space just inside the penalty area. He takes a touch and has time to pick his spot but fails to hit the target with a scuffed shot. That was a let off for the home side.
80 minNiang concedes a free kick in his own half after bringing down Armero. The visitors want a penalty from the cross after Insigne's delivery comes off Montolivo, but replays clearly indicate the ball only made contact with the midfielder's chest.
82 minMilan break down the right as Abate sends a dangerous cross towards the far post. El Shaarawy has a half-chance after controlling well but is eventually crowded out by two covering Napoli defenders.
84 minSUBSTITUTION: Napoli make their final change as Maggio is replaced by on-loan striker Calaio. His introduction will see Armero switch to full-back and give the visitors three options in the final third for the final few minutes.
86 minYELLOW CARD! Pazzini shows his frustration in a dangerous challenge on Zuniga. His late lunge results in a caution and gives Napoli the chance to shoot at goal from 25 yards. Cavani takes but can only send a low curling drive straight into the wall.
88 minSUBSTITUTION: Milan are forced into another change through injury as Abate pulls up with a knock late on. De Sciglio is quickly introduced and will play the closing stages at right-back. Meanwhile Britos becomes the latest player to be booked after wresting Pazzini to the ground.
90 minMontolivo sends a late free kick towards the far post in search of El Shaarawy, who sees his shot from a tight angle blocked. Milan recycle possession quickly as Montolivo drives into the final third and unleashes a low shot that falls well wide of the far post.
90 min+2YELLOW CARDS! Campagnaro and Mexes are both booked for an angry clash after the Napoli defender flew in to a tackle on Niang. Mexes grabbed his nemesis round the neck and is perhaps fortunate not to receive a harsher punishment for the offence.
90 min+3SAVE! Right at the death Armero's cross is tipped away from danger by Abbiati as Cavani comes within inches of making contact the far post. Zuniga keeps the move alive and passes to Calaio, who heads wide unmarked from close range. What an opportunity for the visitors to earn a famous win at the San Siro in stoppage time.
90 min+4Napoli launch one final attack as Cavani and Maggio combine down the right. A looping cross drifts easily towards Abbiati, who launches forward quickly as Milan look to counter, but time has run out for both sides to find a winning goal.
9.42pmFULL-TIME AC Milan 1-1 Napoli
9.44pmIn the end Napoli were content to settle for a point that makes them overwhelming favourites to hang on in the race for second place. Milan missed their chance to make third place secure and now face a fierce fight to earn a place in next season's Champions League.
9.46pmThat just about does it for Sports Mole's coverage of an entertaining clash at the San Siro. Thanks for joining us and be sure to check back in for more Serie A action tomorrow night when Juventus face Lazio.