All eyes will be on Stamford Bridge on Sunday as Chelsea host Manchester United in the Premier League.The Blues are currently at the top of the league table with 29 points from 12 games. They have lost just once in their campaign so far: a 1-0 defeat against Manchester City.The Red Devils, meanwhile, have started life without manager Ole Gunnar Solskjaer. The Norwegian was sacked following a humiliating 4-1 loss to Watford last weekend.With only five wins from 12 games, they're trailing their London rivals by 12 points. They will be eager to stitch up a ruthless winning streak to boost their top-four hopes.Ahead of kick-off, let's look at five key battles that could shape the outcome of the clash:#5 Timo Werner (Chelsea) vs Eric Bailly (Manchester United)Werner's return is a huge boost for ChelseaFresh off scoring off the bench against Juventus in the Champions League, Timo Werner will be soaring in confidence. He has only returned from a lengthy injury spell.Werner has struggled for goals since joining Chelsea last year. However, he made up for that by adapting to a more creative role that saw him register 15 assists last season.Sky Sports Football@SkyFootballTimo Werner's injury time goal put the cherry on top for #CFC as they beat Juventus 4-0 at Stamford Bridge 🔥The heaviest #UCL defeat Juventus have ever had 😮3:25 AM · Nov 24, 20211954147Timo Werner's injury time goal put the cherry on top for #CFC as they beat Juventus 4-0 at Stamford Bridge 🔥The heaviest #UCL defeat Juventus have ever had 😮Either way, Eric Bailly won't have it easy against the German. He will have a rare chance to start in Harry Maguire's absence due to suspension. Bailly will have to muster his A1 game if the Ivorian were to stake a claim in the starting role.#4 Cristiano Ronaldo (Manchester United) vs Thiago Silva (Chelsea)Can the prolific No.7 break the duck against Chelsea?Cristiano Ronaldo has made a sensational return to Manchester United this summer. He has wasted no time in proving his value to the squad, netting 10 goals in all competitions already.Most of his strikes have come at crucial moments, when United needed a late winner or a breakthrough. This demonstrates his ability to step up when the chips are down.The CR7 Timeline.@TimelineCR7Cristiano Ronaldo at Manchester United this season:👕 14 Matches⚽ 10 Goals🅰️ 2 Assists🏅 5 Man of the Match awards🎖️ United Player of the Month September / October🎖️ Premier League player of the month September🥇 Their top scorer in Premier League & Champions League.2:14 AM · Nov 27, 20213735447Cristiano Ronaldo at Manchester United this season:👕 14 Matches⚽ 10 Goals🅰️ 2 Assists🏅 5 Man of the Match awards🎖️ United Player of the Month September / October🎖️ Premier League player of the month September🥇 Their top scorer in Premier League & Champions League. https://t.co/PPj3pBvIzbThere's one catch, though - he's never scored against Chelsea in the league before! Ronaldo's only ever strike against them famously came in the 2008 Champions League finals.As much as he'd be eager to end the drought, Thiago Silva will be tasked with subduing the Portuguese ace once again. It will be an enticing battle between two footballing veterans.