Chelsea: 2020-21 Season Review

It was a season of two halves for Chelsea. Manager Frank Lampard came into it having developed a side brimming with young talent that now needed to be integrated with the summer acquisitions of Timo Werner, Kai Havertz, Hakim Ziyech, Ben Chilwell, Thiago Silva and Edouard Mendy. However, he was unable to ensemble a cohesive team and was swiftly replaced with Thomas Tuchel in January. Switching from a back four to a back three provided a defensive solidity that would see the Blues go on to win the Champions League, as well as achieve top four in the league and reach the final of the FA Cup. This article aims to summarise the key developments to Chelsea’s squad during the 2020-21 season.


Chelsea played 59 games this season: 38 in the Premier League, 13 in the Champions League, two in the League Cup and six in the FA Cup. Below is a graph detailing the changes made per game to their starting line-up across the year. Interestingly, Frank Lampard (4.63) and Thomas Tuchel (4.64) made almost the same average number of changes to their starting line-ups, giving the Blues an overall average of 4.64 changes made per game.

Yet there are some differences between Lampard and Tuchel’s rotation styles. The former fluctuated from a period of little rotation to mass rotation, evidenced through the steep peak and trough in the three-game average. Alternatively, Tuchel preferred to keep his changes within a tighter range (3-7 changes) until the final few games of the season where he narrowed in on a starting XI for the Champions League final.

Could there be mitigating factors for these differences, such as the number of injuries in the squad? The graph below shows the number of Chelsea players missing a game through injury throughout the 2020-21 season. What it shows is that Lampard did, in fact, have to deal with more injuries in his squad than Tuchel, particularly at the beginning of the season. This typically correlates to less rotation as the options available become limited – we saw a similar trend with Manchester City this season. So it is reasonable to put these differences down to mitigating circumstances rather than personal style.


But which players were used the most throughout the 2020-21 season? The below scatter graph plots the availability and utility of Chelsea players across all 59 games, with the medians included on both axes.

  • Availability is classed as the percentage of minutes a player was available for selection out of the total possible minutes in a season (5,310 for Chelsea)

  • Utility is defined as the percentage of minutes played out of the total minutes available for selection

The players above the utility median were most used throughout the season, while the players to the right of the availability median means they were frequently included in the matchday squads. Typically, availability can show if a player has had an injury-free campaign, but it can also show the players who are out of favour with their manager.

Left-backs Marcus Alonso and Emerson are good examples of the latter. Neither player missed a game through injury, according to Transfermarkt, but they failed to make the matchday squad on 21 and 19 occasions respectively, showing how far down the pecking order they were. However, it is worth remembering that Chelsea switched managers part-way through the season, so it was possible for a player to not be used by one manager but feature frequently under the other. For a detailed breakdown of who was favoured under Lampard vs. Tuchel, I wrote an earlier article analysing the difference.

Nonetheless, certain players were integral to both managers. We can find these in the top two quadrants. Some (Cesar Azpilicueta, Jorghino and Mason Mount) continued their presence from the previous season, while others (Edouard Mendy, Timo Werner and Ben Chilwell) were new signings who integrated well into the starting XI. Together, they represent Chelsea’s core.


We see a similar nexus of players when looking at the data on starts for Chelsea during the 2020-21 season. The scatter graph below plots total number of starts (as a percentage) and the average number of starts before omission from the starting line-up. This helps us see who started more frequently, as well as who was rotated more often.

Seven players feature in the top-right quadrant, indicating that they were above the median for both total starts and average number of starts before omission. These were Mendy, Mount, Azpilicueta, Werner, Chilwell, Jorginho and Thiago Silva. Yet the first two are comfortably ahead of the rest. As first-choice goalkeeper, Chelsea’s reliance on Mendy is expected. But the fact both Tuchel and Lampard used Mount so often and rotated him infrequently is a testament to the skills and tactical maturity of the 22-year-old midfielder.


So who had the most involvement in Chelsea’s season? The below graph shows the percentage of minutes played across the season. Fourteen players find themselves above the team’s average of 42.31%, yet none had a percentage higher than 80%, suggesting that minutes were shared out well among the squad.

Mount was Chelsea’s most involved player, with Werner and Azpilicueta the most involved attacker and defender respectively. Others, such as Tammy Abraham, will be disappointed by how little they were involved though. Abraham had a breakthrough season the year before under Lampard, but struggled to make the starting XI under Tuchel. Whether this changes as the German undertakes his first full season as Chelsea boss is a mystery. Olivier Giroud‘s departure means there are attacking minutes up for grabs, however, this depends on a new centre-forward not being signed over summer.

In terms of what to look out for in the 2021-22 season, it will hinge on the formation Tuchel opts for long-term. He implemented variations of a back three in his first five months, which proved successful defensively. Yet the balance felt overly so at times, stifling Chelsea’s offensive potential. So, it is a case of waiting to see whether Tuchel sticks or twists come August 14th.

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