Sunderland have told midfielder Didier Ndong they intend to terminate his contract after the club's record signing went absent without leave in the wake of their relegation to League One last season.
The Black Cats have also indicated their readiness to take legal action to recoup the Gabon international's transfer value should he join another club.
"Sunderland has given notice under its contract with Didier Ndong.
"The player, who was under contract with Sunderland until June 2021, failed to return to Sunderland for pre-season training in July as scheduled, nor in the subsequent months that followed.
"No reason was given for his failure to report and continued absence. As a result, Sunderland has accepted Didier Ndong's repudiatory breaches of contract and notice of the same has been provided to the player.
"Sunderland does so while retaining the right to pursue the player and any club he may subsequently join in relation to compensation for the value of the player."
Ndong, 24, who became Sunderland's record signing when he joined the club for £13.6 million ($17.8 million) from Lorient in August 2016, is understood to have belatedly turned up at the club's training headquarters this week after the prospect of a transfer finally receded amid interest from Torino and Benfica.
He spent the second half of last season on loan at Watford as his parent club slipped out of the Championship, but did not make a single senior appearance.
Sunderland took similar action against central defender Papy Djilobodji earlier this month after he finally returned to Wearside, only to fail to meet the club's fitness standards.