Sunderland have sold Jeremain Lens to Besiktas for £6million after the Turkish giants exercised their option to sign the winger.
Lens has been on loan since last summer and the deal included an option for them to sign the Dutch winger permanently, an option that had to be exercised by the start of March.
Sunderland signed Lens, one of the club's biggest earners, for £12million and while the details of his transfer are officially undisclosed the Echo has learned that Besiktas have paid £6million.
The Echo understands the transfer fee includes the €1.5m loan fee that Besiktas paid last summer.
He will officially join Besiktas on June 1.
Lens, who has made 16 appearances and scored one goals this season, is understood to have signed a four year deal with the Turkish side.
A Sunderland AFC statement read: "Sunderland AFC can confirm that midfielder Jeremain Lens will join Besiktas JK permanently on 1 June for an undisclosed fee.
"The 30-year-old has spent the season on loan with the Turkish Super Lig side, who have now exercised an option to sign the attacker permanently.
"Lens joined Sunderland from Dynamo Kiev in 2015 and made 24 appearances, scoring three times.
"He spent last season on loan at Fenerbache before returning to Turkey with Besiktas last summer."
Lens had been a big-money capture in 2015, costing Sunderland £12million when he was brought to Wearside by Dick Advocaat.
However, he fell out of favour under Advocaat’s successor, Sam Allardyce, and was loaned out to Fenerbahce last season, where he was one of the Turkish league’s most dangerous attackers.
He headed back to Turkey to join Besiktas on loan last summer and has now sealed his permanent move.