|United will need to avoid defeat in Basel in order to book their passage to the knock-out stages after their 2-2 draw against Benfica [GALLO/GETTY]
Manchester United and Manchester City's European Champions League aspirations will go down to the wire after both English Premier League giants suffered wobbles in Tuesday's group action.
Benfica are now top of Group C after the Portuguese held United to a 2-2 draw at Old Trafford.
Basel, who host Alex Ferguson's three-time winners in the final match, are only a point behind after edging out Romania's Otelul Galati 3-2.
Mega spenders City, for their part, slid to a 2-1 loss to Napoli - who had already held them in Manchester - with Edinson Cavani twice on target, leaving coach Roberto Mancini frustrated.
"I don't think we deserved to lose this game (but) we conceded two stupid goals," Mancini.
But he added "I don't think it's finished."
It will be, however, if Napoli polish off still pointless Villarreal of Spain in their final encounter.
With Bayern Munich dispatching Villarreal 3-1 in Bavaria - Franck Ribery twice on target - the Germans win Group A but City have now slipped to third a point adrift of Napoli after the Italians showed true grit to bag a precious win, helped by Cavani's predatory powers.
Napoli went in front on 17 minutes at a jam-packed Stadio San Paolo - where Mancini then a player lost a 1990 World Cup semi as Argentina beat Italy - when Aleksandar Kolarov, tangling with Cavani, deflected in a Marek Hamsik corner.
Walter Mazzarri's men were unable to maintain their advantage, however, and City were back on terms after 33 minutes, Mario Balotelli tapping in a rebound after Edin Dzeko had fed David Silva, whose initial shot home keeper Morgan De Sanctis beat out.
Napoli came out fighting for the second period and within three minutes they had their noses in front for a second time.
Andrea Dossena crossed from the left and Cavani showed great poise to adjust his footing and fire past Joe Hart.
Although United's stalemate with Benfica left them both level on nine points, the Portuguese will progress as winners of Group C if they beat Romanian whipping boys Otelul Galati in their final group game in Lisbon next month by virtue of their better head-to-head record with United.
Benfica have qualified for the group stage regardless of what happens in the final matches - leaving United manager Sir Alex Ferguson in reflective mood.
"The goals were a bit freakish. An own goal and then bad kick out by (keeper) David de Gea. The pass back could have been better but David should have played it into the stands and we didn't hold onto the lead.
"It's a cruel game at times. It will be a hard game in Basel."
Phil Jones put through his own net on four minutes under pressure from Nicolas Gaitan to give Benfica - who had drawn the game in Lisbon 1-1 - the perfect start.
|Real Madrid made it look easy, storming to a 3-0 lead within nine minutes [GALLO/GETTY]
Dimitar Berbatov, dropped from last season's final loss to Barcelona and a peripheral figure this term, levelled on the half hour with Nani's cross tailor made for the Bulgarian, who celebrated his first Champions League goal in three seasons.
Darren Fletcher then put United in front on the hour at the second attempt but Benfica, United's victims in their first European Cup success in 1968 at Wembley, would not lie down and Pablo Aimar equalised from close range just two minutes later.
Inter Milan, champions in 2010, guaranteed top spot in Group B after drawing 1-1 at Trabzonspor leaving them four points clear of their Turkish rivals.
Nine-times champions Real Madrid continued their steamrollering of Group D rivals Dinamo Zagreb, scoring four times in the opening 20 minutes on the way to a comprehensive 6-2 victory.
Real coach Jose Mourinho, whose men went down in the semi-finals to Barcelona last season, is bidding to become the only coach in history to win European football's top prize with three different clubs having lifted the pot both with Porto and Inter Milan.