The Senegal international joined Chelsea from Strasbourg in 2025 and initially returned to the French club on loan. He was recalled in January 2026 after Liam Rosenior, who had previously worked with him at Strasbourg, moved to Stamford Bridge.
The defender was given opportunities in the FA Cup against Wrexham and Hull City, as well as in the Premier League against Arsenal. However, a costly error during Chelsea's Champions League meeting with Paris Saint-Germain proved a turning point.
With Chelsea already trailing 5-2 on aggregate, Sarr failed to deal with a long ball forward in the second leg, allowing Khvicha Kvaratskhelia to break through. He subsequently lost his place in the team, while Rosenior was also dismissed.
Speaking to L'Équipe, Sarr recalled the emotional impact of the experience.
"It was really very difficult – a rollercoaster. I was coming back from the AFCON and I was on a cloud. I started to play, have some good matches, [but] the one against PSG and that error came quickly.
"[Then] no news. No sign of life. The first week was horrible regarding the criticism. And Rosenior, who brought me, was quickly ejected."
The 21-year-old said being left out of the team without an explanation was particularly difficult.
"No longer doing your job, staying on the bench and watching your teammates play was very hard to experience, especially without any explanation. And then, at the World Cup, I thought that I'd be playing, but, without rhythm, I didn't."
Sarr eventually secured a move away from Chelsea, joining Real Sociedad on loan for the 2026-27 campaign. The defender said the opportunity to play regularly had helped him rediscover his enjoyment of football.
"I am living again. I had to be patient and find the best way out [of Chelsea]. I was hungry, very hungry. I wanted just one thing: to play football […] I have rediscovered a bit of the Lyonnais atmosphere. A very good club on a sporting level and a family club, too, that trusts in young players. Real Sociedad is the perfect club for me."
The move has given Sarr the chance to rebuild his confidence and establish himself in La Liga. He has also featured in Real Sociedad's Europa League campaign, with the defender describing the Spanish club as an environment where he feels trusted and valued.