Manchester City have until 2020 to re-sign Enes Unal after agreeing a buy-back clause with Villarreal.
The 20-year-old Turkey international never played a competitive match for City after arriving from Bursaspor in 2015 and he enjoyed several loan spells prior to joining the Yellow Submarine on a five-year deal on Wednesday. He scored 18 Eredivisie goals for FC Twente during the 2016-17 campaign.
But City have reserved the option to take the striker back in the next three seasons and, though the figure remains undisclosed, it is thought to be under £20million.
Villarreal welcomed Unal to the club with a glowing post on their official website, writing: "The Turkish footballer is one of the most promising footballers in Europe at just 20 years of age.
"He is a strong player of great stature, but also possesses great technical ability with the ball at his feet: dribbling, change of pace, a knack for getting in behind the defence and attacking the goal.
"Strong in the air, Unal also has a powerful shot and is dangerous on set-plays, making him the complete footballer at just 20 years old."
