Sunderland have terminated Papy Djilobodji's contract, saying the defender returned to the club late and unfit.
The 29-year-old Senegal international, who was on loan at Dijon last season, put in a transfer request in June.
He failed to report for training in August after Sunderland allowed him to take unpaid leave during July to agree a deal at a new club.
The club said he "comprehensively" failed a fitness test upon his return.
Djilobodji, who was under contract until June 2020, only returned to training in the first week of September after ignoring a number of written requests from the League One club.
In a statement, Sunderland said he was subjected to the same pre-season fitness tests that the rest of the squad went through in July.
Sunderland paid Chelsea £8m for Djilobodji in August 2016, becoming former manager David Moyes' first signing at the Stadium of Light, but his last first-team appearance for the Black Cats was in August 2017.