Manchester United produced an impressive performance against French giants Paris Saint-Germain in their Champions League campaign opener in midweek and will be looking to kick on in similar fashion as they host Chelsea at the Old Trafford on Saturday.The Red Devils have quite a tough set of fixtures to navigate over the course of the next few weeks and will want to use the momentum from their last two wins to take all three points against a talented Chelsea side. Chelsea come to Old Trafford on the back of successive draws against Southampton and Sevilla.We are all set for an exciting encounter as two teams brimming with talent lock horns in a fixture that has become all the more relevant owing to the fact that they're both managed by young managers who used to play for their respective clubs. Both Solskjaer and Lampard will go for nothing less than three points.Without further ado, let's take a look at five key battles that could decide Saturday's matchup.5 key battles - Manchester United vs Chelsea#5 Christian Pulisic vs Aaron Wan-BissakaAaron Wan-Bissaka (left) and Christian Pulisic (right)Aaron Wan-Bissaka took some time to regain the sharpness that set him apart last season after struggling in the opening weeks of the new campaign. Now he looks to have gained full match fitness and looked every bit like himself in Manchester United's wins against Newcastle United and Paris Saint-Germain.Christian Pulisic had been a standout performer for Chelsea last season. However, he is yet to find his form this term and made his return to the side after being sidelined with an injury until the international break. Pulisic, however, hasn't looked his best so far and that has a lot to do with the fact that he's been deployed down the right wing in Chelsea's draws against Southampton and Sevilla.Pulisic loves to operate down the left wing and that's the position from where he scored four goals and racked up four assists post the Covid restart last season. If Lampard decides to play Pulisic down the left flank, then he will be up against Aaron Wan-Bissaka.Aaron Wan-Bissaka has been exceptional for Manchester United particularly against pacy wingers and has dealt admirably with the threat posed by the likes of Raheem Sterling and Kylian Mbappe in the past. This should be a test of both Pulisic's and Wan-Bissaka's abilities.No player made more tackles in the Champions League this evening than Aaron Wan-Bissaka (6).Spider-Wan shuts down a left-hand side worth more than €400m. 🕸 pic.twitter.com/aHQtS8nVca— Squawka Football (@Squawka) October 20, 2020#4 Alex Telles vs Reece JamesAlex TellesOne of Manchester United's latest acquisitions, Alex Telles, put on an impressive display against Paris Saint-Germain in his debut. Telles whipped in some delightful balls from the left flank and worked hard throughout. He has also been placed on corner-kick duties and is sure to whip in a couple beauties on Saturday.If Manchester United go with a back three, then Alex Telles will be up against Chelsea right-back Reece James. Reece James loves to bomb forward and get involved in attack and he was one of Chelsea's best players in their win over Manchester United in last year's FA Cup semi-final.If both these players are named in the lineup, we could see an excellent contest down both flanks as neither Telles nor James are wing-backs who like to concede a yard to the opposition.Should Reece James keep his place in the Chelsea starting XI v Man U?The answer for me is yes, in fact I'd keep the same back line setup that kept Sevilla at bay.Cohesion and clean sheets are a byproduct of stability... as well as having a decent goalie of course.Thoughts pic.twitter.com/AJLgfXehSs— Mark Worrall (@gate17marco) October 23, 2020