After an excellent 2021 that saw them named club of the year, Chelsea will now look to build on that success heading into the new year.Chelsea were able to enjoy great success after a change in personnel at the helm of affairs that saw them appoint Thomas Tuchel as manager. The club went on to win the UEFA Champions League and UEFA Super Cup in 2021. They also broke their transfer record to sign striker Romelu Lukaku from Internazionale.The end of 2021 saw a mixture of injuries and COVID-19 derail Chelsea's campaign in the Premier League. However, strong performances will get them back in the race, and also help them make a deep run in the Champions League. Chelsea are also alive in both domestic cup competitions, and also have the FIFA Club World Cup to play for.Midfielder Saul Niguez has not considered because he's unlikely to be at the club beyond the season. With youngsters Conor Gallagher and Billy Gilmour doing well on loan, the services of the Spaniard will likely not be retained by Chelsea.On that note, here's a look at five Chelsea players who must improve this year to help the club achieve their goals.#5 Malang SarrBrentford vs Chelsea - Premier LeagueHaving narrowly missed out on a summer loan move to Greuther Furth, France U-21 international Malang Sarr was drafted in by Tuchel to bolster his defence. The defender, who was on loan at FC Porto last season, found himself playing games for Chelsea.Sarr was given a handful of games to impress the Chelsea boss. Unlike fellow youngster Trevoh Chalobah, the Frenchman was unable to nail down a place in the squad.Before the season-ending injury suffered by Ben Chilwell, it was decided to loan out Sarr during the January transfer window. The injury to Chilwell changed the defender's fate, as Tuchel recognises the importance of keeping the squad as big and competitive as possible.Absolute Chelsea@AbsoluteChelseaMalang Sarr is attracting interest from Torino, Strasbourg, Watford & West Ham but is in 'no rush' to leave #Chelsea and could end the season at Stamford Bridge.[via @Santi_J_FM]1:35 PM · Jan 5, 202257341Malang Sarr is attracting interest from Torino, Strasbourg, Watford & West Ham but is in 'no rush' to leave #Chelsea and could end the season at Stamford Bridge.[via @Santi_J_FM]Sarr should get chances to impress in 2022, and must be prepared to take them with both hands. The club will be competing on multiple fronts, and Sarr is likely to get games at Chelsea in the second half of the season.Considering the contract situation of Antonio Rudiger, Sarr could position himself well in the eyes of the coaching staff.#4 Ross BarkleyBrentford vs Chelsea - Carabao Cup Quarter FinalRoss Barkley has had a tumultuous season at Chelsea. Considered on his way out of the club in the summer, he continued as a Chelsea player, as there was no suitor for his services. The Englishman has made 11 appearances for Chelsea in all competitions, but has no goals or assists to show for his efforts.At 28, it is expected that Barkley should be at the top of his game at Chelsea, but the midfielder has had a rather disappointing spell at the club. The recent injury problems suffered by the team in midfield make it unlikely that Tuchel would let Barkley leave the team in the winter.Simon Phillips@siphillipssportChelsea are reportedly open to offers for Ross Barkley in January and he could go on a permanent deal...chelsea-news.co/2021/12/chelse…08:52 AM · Dec 31, 2021152881Chelsea are reportedly open to offers for Ross Barkley in January and he could go on a permanent deal...chelsea-news.co/2021/12/chelse… https://t.co/3mL0D00ldLBarkley must be ready to deliver much more quality in 2022 to help Chelsea compete in all fronts. He must now come through for the side with positive contributions to aid their ambitions. In the process, he could possibly position himself for a national team return ahead of the FIFA World Cup.