The 25-year-old French defender failed to make a lasting impact after joining the club in 2020.
Despite his potential, Sarr struggled to break into the first team, spending much of his time on loan at Porto and AS Monaco.
After returning from Monaco in the summer of 2023, Sarr found a new manager in Mauricio Pochettino and a slew of new signings.
Yet, he was almost invisible in the squad.
When asked about Sarr's future in a press conference, Pochettino's response was blunt: "Who is that?"
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Sarr reflects on the harsh reality of his Chelsea experience, admitting that Pochettino's dismissal of him hurt.
"I took it badly," Sarr confessed to L'Équipe. "It shouldn't have happened. He knew me. He even tried to sign me at Tottenham. I didn't ask for an explanation."
Throughout Pochettino's first season at Chelsea, Sarr didn't see a single minute of action.
By the end of the campaign, both he and Chelsea parted ways, with his contract mutually terminated, paving the way for him to join RC Lens on a free transfer.
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Despite the disappointment, Sarr insists he has "no regrets" about his Chelsea journey, though he does acknowledge that his time at Stamford Bridge felt like a lost opportunity.
Since joining Lens, Sarr has featured six times across all competitions and made his second start in Ligue 1 in a 3-1 loss to Olympique de Marseille on Saturday.
Sarr spent four years at Chelsea but his time there featured two loan spells, instantly going to Porto for a year and returning in 2021.
That year, he made his Chelsea debut during a 1-1 draw with Aston Villa in the League Cup.
In August 2022, Sarr went on loan to Monaco with an option to buy. During the 2023-24 season, he was excluded from Chelsea's first team, training with the Under-21s and missing out on a proposed loan move to Le Havre.
In July 2024, his contract with Chelsea was terminated by mutual consent, and he signed a two-season deal with Lens.
Sarr has made four appearances in Ligue 1 this season and despite his time at Chelsea not going to plan, he admitted he has 'no regrets' about the move.