However, the two-time European champions held out to earn their first Group C point of the campaign.
Below you can read how the action unfolded with Sports Mole's live text updates.
6.48pmEvening, all. Group C is one of the most open in this season's Champions League. All four teams will fancy their chances of qualifying, but tonight could be last chance saloon for Benfica in Monaco.
6.51pmThe Portuguese outfit have lost to Bayer Leverkusen and Zenit St. Petersburg in their opening two games and know that another defeat at the Stade Louis II will all but end their last-16 hopes.
6.54pmIt has been a more positive start for Monaco and Leonardo Jardim, whose four point-haul in Europe is helping him overcome the doubters following a stuttering start to the Ligue 1 campaign.
6.57pmOnly appointed as successor to Claudio Ranieri in May, Jardim is already under pressure, with the French big spenders only 10th in the table after four defeats in 10 games, having yet to show that they can be title contenders without departed Colombians Radamel Falcao and James Rodriguez.
6.59pmMonaco are already reportedly lining up a return for Arsenal manager Arsene Wenger, and so progress in the Champions League could count a lot for Jardim's job security come next summer.
7.02pmHaving left Benfica's great rivals Sporting Lisbon to join Monaco, Jardim may have some inside knowledge of their Portuguese visitors, and will not be fooled by their slow European start.
7.05pmJorge Jesus's side have started their domestic title defence with 19 points from a possible 21, which is a great return considering that he too is having to overcome the loss of several star men.
7.08pmLazar Markovic to Liverpool and Ezequiel Garay to Zenit were two damaging departures, while Oscar Cardozo, goalkeeper Jan Oblak and skilful midfielder Andre Gomes have also moved on.
7.10pmSo who do Benfica have to call upon tonight? Let's take a look at the team news and find out!
7.17pmCesar, Jardel and John are all missing for the visitors through injury, who make two changes as Samaris and Derley drop out of midfield to be replaced by Enzo Perez and Andre Almeida. Former Manchester United striker Bebe, who is yet to play this season, is among the substitutes.
7.20pmSix-goal top scorer Talisca will be Benfica's main threat and has two very good creative players in the shape of Eduardo Salvio and Nicolas Gaitain to provide him with chances from out wide.
7.23pmMonaco make four changes from the side which beat Evian 2-0 at the weekend. Lacina Traore is unavailable, while Tiemoue Bakayoko, Yannick Ferreira Carrasco, and Valere Germain are out.
7.26pmNabil Dirar, Lucas Ocampos and Geoffrey Kondogbia are back in the starting XI, but the headline recall is that of former Tottenham Hotspur and Manchester United forward Dimitar Berbatov.
7.28pmBerbatov has two goals in nine games this season, and finding the net has been a problem for in general for Monaco, who have only five goals in their starting lineup so far this season.
7.30pmThey do have a Champions League winner in their ranks, though, in former Chelsea defender Ricardo Carvalho. The 36-year-old was part of the Porto side who beat Monaco in the 2004-2005 final.
7.33pmThe French side's strength is in central midfield, where the passing ability of Joao Moutinho, running power of Geoffrey Kondogbia and experience of Jeremy Toulalan makes for a nice blend.
7.35pmHISTORY: Benfica are two-time European champions, with Eusebio in his prime inspiring them to consecutive victories in the early 1960s. Monaco's best finish is runners-up in 2004-2005.
7.38pmThis is the first ever Champions League meeting between the sides, but Benfica have plenty experience facing French opposition, against whom they have won half of their 26 European matches.
7.41pmONE TO WATCH: Joao Moutinho. A technically-gifted player with a great passing range, the Portuguese midfielder, formerly of another of Benfica's rivals - Porto, is key to how Monaco play and is also the scorer of their only Champions League goal so far this season.
7.43pmPREDICTION: Benfica know the importance of this game and, playing away from home may just suit them. They are great on the break and could cause a surprise. 2-1 to the visitors.
1 minKICKOFF: Szymon Marciniak and his Polish officials signal for the game to begin...
4 minMonaco have started on the front foot, having plenty of the ball, which is what you would expect. That might suit Benfica, though. They are not good travellers traditionally, but boast a great counter-attacking threat and will look to break quickly when they overturn possession.
5 minMISS! Ocampos misses an open goal and a chance to put Monaco ahead! Berbatov beats the offside trap and unselfishly squares for his teammate, but the ball takes a bobble off the surface and Ocampos skies over from eight yards. He had most of the goal to aim at, but barley made contact.
8 minBOOKING: The pacey Dibar gets in behind Eliseu and clear on the right wing, and Benfica's left-back takes an early yellow card for the team by pulling him back to concede a free kick.
11 minBenfica's first notable attack sees Lima, the artist formerly known as Rodrigo, burst to the right byline and drill in a cross towards Talisca which is cleared at the near post by Carvalho.
13 minA couple of free kick opportunities have gone to waste for Monaco. Moutinho has chosen to loop them high in the air rather than whip them in with pace and Luisao has found them easy to deal with.
16 minOf course there are seven other Champions League ties in process, including Liverpool versus Real Madrid and Arsenal in Anderlecht. I will keep you updated with the English side's progress.
18 minMoutinho's deliver from a corner this time has more zip behind it, but again the towering figure of Benfica captain Luisao is there at the near post to get in front of Kondogbia and head clear.
19 minDelightful feet from Moutinho creates room for him to turn his way into the box before shifting across to Ocampos, whose first touch sees the ball roll away from him. In an attempt to win it back, he catches Gaitan on the knee with a high boot and is perhaps lucky to escape without a caution.
21 minBenfica show their ability to break for the first time as Gaitan is released down the left. His deep cross is towards Salvio, who slices a difficult chance on the bounce way off target.
23 minCarvalho makes an important intervention to block a goal-bound shot from Lima.
24 minUPDATE: Liverpool kept him out for 23 minutes but it seems that nothing can stop Cristiano Ronaldo at the moment! He has given Madrid the lead at Anfield following a lovely passing move.
26 minBOOKING:Lisandro Lopez follows Eliseu into the book after catching Berbatov in the face with his boot in the follow through of a clumsy mistimed tackle - not his first, either.
28 minSHOT! Not known for his goalscoring ability, Toulalan pops up with a 25-yard shot, having been teed up by Moutinho, which Artur holds comfortably at chest height.
30 minIt's now Benfica's turn to try their luck from distance, but Subasic is not going to be troubled by that wayward effort from Almeida, who thrashes heigh and wide with a left-footed half volley.
31 minUPDATE: It's looking ominous for Liverpool now, with Karim Benzema having doubled Madrid's lead on Merseyside before the half-hour mark. The Reds must get to half time further unscathed.
33 minSUBSTITUTION: Back in the French principality, bad news for Berbatov, who instantly signalled to the bench that his night was over after appearing to pull a muscle attempting an ambitious volley. The grimacing Bulgarian limps off to be replaced by the more direct Anthony Martial up front.
35 minWith Monaco already finding goals tough to come by, Berbatov's withdrawal will do them no favours. Martial's pace will present Benfica's defence with something different to think about, though.
36 minBOOKING: Half a chance for Benfica, but Lima does not commit to putting his head in to reach a Gaitan flick on as Carvalho's flying boot came to meet it at the same time. Salvio is booked shortly in the aftermath for tripping Ocampos as Monaco threatened a counter-attack of their own.
39 minSAVE! Benfica take corner short. Salvio returns the ball to Talisca, who whips in a dangerous low ball which Lima sweeps towards goal, only for Subasic to make a great reaction stop. The attacker had got in front of his man at the near post and must have thought he had scored before Subasic's good work.
42 minUPDATE: It's all over bar the shouting before half time at Anfield, where Liverpool are being dealt a Champions League lesson by holders Madrid. Benzema's second has made it 3-0.
44 minGaitan has been lively without quite having yet had an impact on proceedings. The winger has made several promising runs which have ended either at the second man or a poor pass.
45 minWe are now entering TWO minutes of first-half stoppage time at the Stade Louis II...
45+1 minThe visitors launch a long throw into the box which Raggi gets up well to head clear.
8.38pmMonaco and Benfica enter the break goalless at the Stade Louis II, but they really shouldn't be. Lucas Ocampos missed a glorious chance for the hosts only five minutes in when he had an open goal to aim at, but sliced wide from Dimitar Berbatov's pass following a horrible bobble.
8.41pmClear-cut opportunities have been difficult to come by apart from that, although Monaco goalkeeper Danijel Subasic was forced into a good reflex save from Lima after a delightful Talisca cross.
8.44pmThe hosts, hit by Berbatov's withdrawal due to a muscle problem, faded after a promising start, while Benfica grew into the half as it went on. Nicolas Gaitan is a particular bright spark, and the longer that the score stay goalless, his pace will be a greater counter-attacking threat.
8.46pmUPDATE: Real Madrid lead Liverpool 3-0 after 45 minutes at Anfield. Arsenal are goalless in Anderlecht, while elsewhere in Group C, Bayer Leverkusen and Zenit are deadlocked at 0-0.
8.48pmSTATS: Benfica had more of the ball than anticipated in the first half, with 57% possession. They only managed to convert that into one shot on target - the same number as their toothless hosts.
46 minKICKOFF: We are back underway, with both sides unchanged for the second half...
48 minCLOSE! Dibar threads a nice ball through the two Benfica centre-backs which Martial runs onto, before striking first time across goal and a yard wide of the far post. Really good effort.
49 minSalvio battles with Kurzawa to the right byline and digs out a cross which Lima just fails to reach.
51 minThe game is slowly opening up. A tidy Monaco move ends up with Artur collecting a cross from Dibar, who has begun the second period promisingly cross and starting a quick Benfica break. Salvio's driving run comes to nothing when his through ball towards Talisca is intercepted.
53 minAnother injury concern for Monaco as Moutinho requires attention to his shoulder following a nasty fall. The damage appears not too serious, though, and the midfielder should be fine to resume.
56 minGaitan wonderfully backheels to Talisca and then collects a return pass from the striker to hang a cross up to the back post, where Salvio nods across, but Carvalho gets in front of Lima and is fouled.
59 minSAVE! Subasic produces a second fine save to keep Monaco level. Dibar's foolish attempts to try to keep the ball in play near his own byline presents Gaitan with the ball, and the winger evades two challenges as he dances into the box before seeing a powerful thrash palmed away by Subasic.
62 minSUBSTITUTION: Jardim makes his second change as Monaco villain Ocampos is replaced by Ferreira-Carrasco. The winger will have nightmares about that open goal tonight.
64 minUPDATE: Two quick goals have put Bayer Leverkusen in control of Zenit in the other Group C match.
65 minNot for the first time this evening, Talisca is fortunate to escape without a card, this time for a cynical trip on Fabinho. Raggi heads the resultant Moutinho free kick over from an offside position.
68 minCHANCES! Two chances in quick succession for Benfica, as Gaitan and Talisca lead a break which eventually ends with Salvio shooting low at Subasic. He perhaps should have pulled back to Gaitan in the middle, rather than shoot. The visitors get another bite at the cherry when Perez tries to place a layoff into the bottom corner from 25 yards, but Subasic is equal to it again as Benfica knock on the door.
71 minCHANCE! Benfica have another sight of goal, and this time Salvio is aware enough to pull a cross back to the edge of the box. A poor first touch from Perez takes the ball out of his control, and he is forced into a volley which was always going to go over the bar as he leaned backwards.
72 minCHANCE! Monaco threaten out of nowhere as Moutinho finally produces a good set-piece delivery. Kondogbia lost is marker in the middle, but glanced a few yards wide of the post.
75 minA few things to update you on as Gaitan slices a left-footed volley from unlikely angle wide. Carvalho has been booked for going through the back of Almeida, and former Man United striker Bebe has been brought on by Benfica in a straight swap which saw lone frontman Talisca hooked.
77 minRED CARD! Benfica defender Lisandro Lopez is sent off for a stud-first lunge on Moutinho, who was caught quite badly by the follow through. The centre-back had already been booked, but referee Szymon Marciniak shows him a straight red card, and he can have few complaints.
78 minThat could prove to be the pivotal moment in this match. Benfica were certainly in the ascendancy and looked the most likely to grab a winner, while Monaco may have felt that escaping with a point on an off night would have been satisfactory. That has all changed now. Jardim's boys will want all three.
80 minSUBSTITUTION: Lisandro Lopez's dismissal is a double blow for Benfica, as it means that their most threatening attacker, Gaitan, has had to be sacrificed to accommodate defender Cesar.
82 minMonaco are suddenly abuzz with opportunity, sensing that this match is there for the taking. The pattern for the final 10 minutes seems to have been set, with Benfica penned back in their half.
84 minSUBSTITUTION: Jardim makes his final change, swapping Moutinho for creative midfielder Bernardo Silva, who came through the ranks at Benfica and left to join Monaco in the summer.
85 minUPDATE: A quick update from Belgium, where Arsenal's qualifying chances are on course for a major hit. Anderlecht lead 1-0 with two minutes plus stoppage time remaining there.
86 minArtur comes some distance off his line to punch clear a Monaco free kick. The ball falls to Kondogbia, who skies a first-time volley over the top. Difficult chance, but he never looked in control of it.
88 minUPDATE: Arsenal have equalised in Belgium! Left-back Kieran Gibbs the unlikely scorer.
89 minSUBSTITUTION: Two minutes plus the rest for somebody to find a winner here. Benfica hope to live and fight another day and bring on Andreas Samaris's fresh Greek legs for Perez in midfield.
90 minUPDATE: Amazing late turnaround from Arsenal as Lukas Podolski scores what will surely be the winner against heartbroken Anderlecht. Will there be late drama in Monaco too?
90+1 minFIVE minutes of added time is signalled as Maxi Pereira concedes a corner at the far stick.
90+3 minMISS! That may have been THE chance for Monaco! Ferreira-Carrasco's corner is superb, and Raggi had got round the back of Cesar, but headed down and narrowly wide from six yards!
90+5 minBOOKING: Ferreira-Carrasco tugs back Pereira after being dispossessed by the full-back and is cautioned for his troubles. That should waste enough time for Benfica to get home safely.
9.43pmBenfica survive 20 minutes with 10 men to pick up their first point in Group C. They had looked the most likely at Stade Louis II before Lisandro Lopez's red card, but then had to hold out for a draw late on. Monaco will still look to that early Lucas Ocampos miss and feel that they should have won this match.
9.44pmChampions League Group C remains wide open at the halfway point. Benfica are bottom and have a lot of work to do, but their late rearguard means that they still have hopes of qualifying. Monaco, second behind Leverkusen, who beat Zenit 2-0, will fancy their chances, but need to start scoring.
9.46pmThat's it from me. Thanks for joining Sports Mole for tonight's Champions League coverage, and be sure to stick with us for reaction to all eight matches.