Signed on a free transfer in 2020, the Blues were hopeful that they were getting value for money for a player who had previously starred for Nice.
However, aside from proving to be an important squad member during the 2021-22 campaign under Thomas Tuchel, Sarr has spent his time out on loan or in the wilderness.
Indifferent temporary stints have come at Porto and Monaco, before the 25-year-old missed the entire 2023-24 season having been left out of contention by Mauricio Pochettino.
There has been little explanation as to what has happened to the centre-back with no official updates having been provided by the Premier League club.
In a positive development for all concerned, though, a report has emerged that Sarr will soon be signing for a new club.
Lens in line to sign Sarr
According to Foot Mercato journalists Santi Aouna and Sebastien Denis, Lens and Sarr have reached an agreement having already held discussions.
While nothing has been disclosed over a transfer fee, the assumption is that Chelsea will be happy to allow Sarr to leave on a free transfer or low fee.
The report adds that Sarr will pen a two-year contract with Lens, who are said to view him as an important addition ahead of a season which they will hope will feature Europa Conference League football.
Lens will hope that Sarr can recapture the form that he showed during his stint with Nice between 2016 and 2020, where he made 119 appearances.
What did Sarr bring to Chelsea?
Although Sarr was never first choice under Tuchel, it gets forgotten that he put in a man-of-the-match performance on his Premier League debut when Chelsea recorded a 1-0 win at Brentford.
His next 90 minutes in the top flight did not come until a fixture at Manchester City in January, Chelsea only going down by a 1-0 scoreline. That was followed by wins and clean sheets versus Tottenham Hotspur and Crystal Palace respectively.
Sarr would make 21 outings in all competitions during 2021-22. In nine EFL Cup and FA Cup matches in which he started, Chelsea won every game.
Furthermore, minutes also came in each of the Club World Cup encounters against Al-Hilal and Palmeiras, the Blues winning the trophy for the first time.
Not much will be made of Sarr's pending exit, yet it was a rarity that matches were lost when he made an appearance.