Sarr is expected to feature in Strasbourg's home match against Paris St‑Germain on Sunday night, but it is likely to be his final appearance for the Alsace club.
Last January Chelsea completed their first permanent signing from Strasbourg since the two clubs came under the same BlueCo ownership, in a £12m deal.
Sarr made one substitute appearance for Chelsea as they won the Club World Cup in the summer before returning to Strasbourg on loan in August.
Recently appointed Chelsea head coach Liam Rosenior described Sarr as "my son", with "scary" potential to become "world class" during his spell in charge of Strasbourg last season.
The defender's expected return, after winning the Africa Cup of Nations as a starter for Senegal in January, is likely to provoke anger among Strasbourg supporters.
Protests from a minority of fans earlier in the season intensified when Rosenior left the club to replace Enzo Maresca, who had fallen out with senior figures at Chelsea and departed on New Year's Day.
Chelsea's defence has not performed at the level of their attack in the Premier League this season and they rank only 11th for expected goals (xG) against despite having conceded the joint-third fewest goals.
Yet Chelsea can strengthen their defence in the short term by bringing back a player Rosenior likes working with, while also moving to secure long‑term target Jacquet.