PARIS (AFP) - Manchester United and Manchester City can both seal their places in the knockout stages of the Champions League with victories over Benfica and Napoli respectively. They could be joined in the last 16 by German giants Bayern Munich, who need just a point at home to pointless Spanish side Villarreal, 2010 champions Inter Milan, who also need a point at Turkish side Trabzonspor, and Dutch side Ajax if they beat Lyon. Both United and City face tough tasks nevertheless to secure their places as Benfica are equal on points with the former while Napoli gave City a fright in their opening match - a 1-1 draw at City - and are tough to beat at home. United warmed-up for the visit of Benfica with a 1-0 win away at Swansea to keep the pressure on City at the top of the Premier League. However, what really pleased Sir Alex Ferguson was the manner in which his defence performed after a series of worrying slips in recent weeks. "Keeping clean sheets has been an integral part of our success and we have been careless with our defending," the 69-year-old Scot told MUTV. Benfica - who held United 1-1 in Lisbon - will have to achieve something no other Portuguese side has done before in 10 Champions League matches at Old Trafford - namely win there. However, they are yet to lose away from home in Europe this season and in Paraguayan striker Oscar Cardozo have a marksman of the highest quality. Manchester City will also have to pull off quite a feat to prevail in Naples as the hosts are unbeaten in all 10 European matches they have contested since returning to continental competition in 2008. However, City manager Roberto Mancini believes his side are acclimatising to the higher level of the Champions League, though, he accepts that his opponents will not be a pushover. His Napoli counterpart Walter Mazzarri is happy with the way his team are playing but realises City will pose a big challenge. "If we keep expressing ourselves at this level then I'm sure we'll win a lot of games," said Mazzarri. The Bayern hierarchy, though, will be looking for a vastly different level of performance than the one that saw them lose 1-0 to champions Borussia Dortmund on Saturday. "We have to banish a painful defeat," said club chairman Karl-Heinz Rummenigge. They will have to do so without injured Dutch playmaker Wesley Sneijder, but will hope for the same outcome as the 1983/84 UEFA Cup clash when they lost the first match 1-0 but went back to the San Siro and won 2-0.