Turkish midfielder Kerim Frei has returned to his home country to join Istanbul Başaksehir FK.BCFC
The 23-year-old has agreed a four-year contract with the 2016/17 Super Lig runners-up.
His departure comes just six months after he joined Blues from Besiktas in January 2017, having being brought in by former manager Gianfranco Zola on a three-and-a-half-year deal.
Frei subsequently found his playing time at St. Andrew's limited during the second half of the 2017/18 campaign, and he made just 13 appearances in total, with ten of those coming off the substitutes' bench.
His last start was during the 2-0 Sky Bet Championship home defeat to Burton Albion in April.
Frei has passed his medical and will sign his contract at a presentation on Friday morning.