Manchester United travel to Chelsea in a key Premier League game that could be crucial to both teams’ top-four hopes.Chelsea still lack the finishing in the final third, but come off a fine win at Atletico Madrid in the Champions League in midweek. Manchester United, meanwhile, dismantled Real Sociedad with ease in the Europa League. The Red Devils have lost just once since January and will look to continue their rich vein of form.Bring on the Blues! 👊#MUFC #PhotoOfTheDay— Manchester United (@ManUtd) February 27, 2021With games coming thick and fast, Chelsea face Manchester United and Liverpool in the next few days as the battle for the top four intensifies. The Blues haven't beaten Manchester United in the Premier League since November 2017, while the reverse fixture at Old Trafford ended in a goalless draw.Thiago Silva is the only injury absentee for Chelsea as he continues his recovery from a muscle injury. However, Manchester United are without a few key players, with Paul Pogba being the biggest name. Phil Jones and Juan Mata are also absent, but Edinson Cavani, Donny van de Beek and Scott McTominay are expected to be available.On that note, let's take a look at five key player battles that could determine the outcome of the game.#5 Mateo Kovacic (Chelsea) vs Fred (Manchester United)Mateo Kovacic has been sensational under Thomas Tuchel.Chelsea's best player under their new boss Thomas Tuchel has been Mateo Kovacic, without a doubt. The Croatian's dribbling ability, positional awareness and ability on the ball has made him a key player under the new Chelsea tactician.Kovacic has the highest dribbling success rate in the Premier League and is second only to PSG's Marco Verratti in the top five leagues. His quality in tight spaces also makes him an integral player in Tuchel's team.Mateo Kovačić under Thomas Tuchel in the Premier League this season per 90 compared to Frank Lampard:◉ More Big Chances Created◉ More chances created◉ More penalty area entries◉ More take-ons completed◉ More shotsPlaying with more freedom in the middle.— Squawka Football (@Squawka) February 26, 2021Against Manchester United, Kovacic will likely be up against Fred in midfield. Unlike Kovacic, when the ball is at his feet, Fred favours simplicity, which can be his undoing at times.Nevertheless, Fred is quick to close down opponents. His willingness to press and win the ball back could be key in his battle against Kovacic.#4 Callum Hudson-Odoi (Chelsea) vs Luke Shaw (Manchester United)Luke Shaw has been Manchester United's unsung hero in recent games.Luke Shaw has been a key player for Manchester United this season. The English full-back has worked on his fitness and is blossoming with regular game-time.The 25-year old has managed five assists in the league this season, providing an attacking outlet for Manchester United from the left flank. Shaw has been solid defensively as well, with Manchester United's decent defensive record testimony to that.Luke Shaw has now assisted four goals in his last three Premier League games. 🅰️🅰️ vs. Southampton🅰️ vs. Everton 🅰️ vs. West Brom Manchester United’s new playmaker. 😅 pic.twitter.com/hu7em6W3in— Squawka Football (@Squawka) February 14, 2021At Stamford Bridge, Luke Shaw will be against one of Chelsea's former academy product Calum Hudson-Odoi.The 20-year old has been a key player for Chelsea, especially in recent games. Hudson-Odoi will be full of confidence after an epic display against La Liga leaders Atletico Madrid in the Champions League.The winger loves to get into one-on-one situations and will look to take on Luke Shaw and get the better of him.