After a transfer ban prevented Chelsea from making any additions during the 2019-20 season, the Blues spent big in the summer of 2020 to strengthen their squad.The club spent more than £200 million on seven players to close the gap on the likes of Liverpool and Manchester City in the Premier League.While the players were signed by Frank Lampard, they could not prevent the Englishman from getting sacked in January after a string of poor performances.Former PSG boss Thomas Tuchel was appointed by the club and the German did a brilliant job at the helm, guiding Chelsea to a fourth-placed finish in the league. He also took them to the FA Cup final, which they unfortunately lost. However, his biggest moment came in the Champions League when he took the Blues all the way to the trophy.Chelsea have started the 2021-22 season under him in brilliant fashion. The Blues clinched the UEFA Super Cup in August while they are top of the Premier League during the October international break.How have the 2020 summer signings fared so far for Chelsea?Given that it's been more than a year since Chelsea's summer spending spree, not all of the seven signings have worked out exactly as expected for the Blues. While some have performed brilliantly, others have had a mixed career so far and have not made the same impact that fans would have hoped for.Here we have decided to rank the seven summer signings based on their performances in the Chelsea shirt so far:#7 Malang SarrChelsea v Aston Villa - Carabao Cup Third RoundThe arrival of Malang Sarr on a free transfer was an exciting prospect for the Chelsea fans. Only 21 at the time, the defender had already made more than 100 senior appearances for OGC Nice and was considered one of the most talented young players.With Chelsea having a number of options at centre-back, the Blues decided to send him on loan to Porto so he can continue his development.Sarr, however, did not quite live up to the expectations in Portugal. The French centre-back failed to dislodge the club's first-choice options and managed to make only 19 appearances in all competitions for the side. Only nine of these appearances came as starts.Sarr returned to the club this summer and was expected to go out on loan again. However, Chelsea failed to find a club for the youngster before the end of the transfer window.Though initially not part of Thomas Tuchel's plans, Sarr did make an appearance for Chelsea in the Carabao Cup against Aston Villa. He will however be expected to go out on loan again once the transfer window opens in January.Chelsea FC USA@ChelseaFCinUSAMalang Sarr is making his Chelsea debut today 👏11:21 AM · Sep 22, 20213474157Malang Sarr is making his Chelsea debut today 👏 https://t.co/x3tBuUqyeu#6 Hakim ZiyechChelsea v Tottenham Hotspur - Pre Season FriendlyA lot was expected from Hakim Ziyech after his £36 million move from Ajax last summer. The Moroccan has struggled with injuries at Chelsea so far while his performances have been largely inconsistent when given the opportunity.After arriving at Chelsea, Ziyech didn't make his official debut for the club until October last season, due to a knee injury he picked up in pre-season. He looked brilliant early on with impressive performances against Burnley and Sheffield United. It looked like Ziyech would light up the Premier League with his excellent passing, crossing and playmaking abilities.However, after suffering a hip injury in December, things have not been quite the same for the 28-year-old. He did play a few times under Thomas Tuchel and scored some crucial goals in the second half of the campaign. However, Ziyech has not been able to have a consistent run in the team.After having a bright pre-season before the 2021-22 campaign, it looked like Ziyech would showcase his true abilities this season. However, the former Moroccan has been largely unimpressive with his performances so far.Ziyech has made just 11 goal contributions (seven goals & four assists) in 45 appearances for the Blues. The winger needs to improve his performances pretty soon, or he may face an early exit from his Chelsea career.Lebo Kgaye@LebogangKgayeJust thought about it and Hakim Ziyech has had to deal with a lot of stuff since his chelsea move.Multiple injuries at awkward times, his best friend changed clubs plus he's had a fallout with his national team coach.Footballers are humans too, hope Ziyech comes good though1:39 AM · Oct 4, 2021Just thought about it and Hakim Ziyech has had to deal with a lot of stuff since his chelsea move.Multiple injuries at awkward times, his best friend changed clubs plus he's had a fallout with his national team coach.Footballers are humans too, hope Ziyech comes good though https://t.co/mirzPUAI8x#5 Kai HavertzTottenham Hotspur v Chelsea - Premier LeagueOne of the Bundesliga's brightest young talents, there was a lot of excitement among Chelsea fans when Kai Havertz joined from Bayern Leverkusen for a then club record £72 million. The German had excelled at Leverkusen, scoring 46 goals and assisting 29 in just 150 appearances for the club.However, Havertz has struggled to adapt to English football, often looking lightweight and lacking the confidence he was filled with in the Bundesliga.He struggled in the first half of last season under Frank Lampard, albeit a COVID-19 infection was one of the main reasons that took toll on his performances. He did, however, show a steady improvement in the second half of last season under new manager Thomas Tuchel. His biggest moment came towards the end of last season when he scored the winner in the Champions League final for the Blues.Bawku Naaba cfc 💙@BawkuCfcKai Havertz was keen to ensure that he didn’t become a meme in the ucl final for Chelsea ! 👊💙8:52 AM · Oct 10, 2021473Kai Havertz was keen to ensure that he didn’t become a meme in the ucl final for Chelsea ! 👊💙 https://t.co/FkWOZNsnzbHowever, Havertz has struggled to show the same form this season that he showed towards the end of last campaign. Barring one excellent header against Liverpool, Havertz has been largely on the periphery of matches and hasn't taken the chances coming his way.Havertz has so far managed to register 10 goals and 10 assists in 54 appearances for the Blues. Still only 22, Havertz has a lot of time on his side. However, considering the competition for places in the Chelsea squad, he will need to improve his performances pretty soon.