Kevin-Prince Boateng's first start for Besiktas ended on a losing note as the Black Eagles were defeated 1-0 by Istanbul Basaksehir courtesy of Demba Ba's goal.
Boateng made his debut last week, coming off the bench to score in the 3-0 victory over Gaziantep.
This time, he made the starting XI, but could not replicate the same form.
Rather it was Demba Ba who hit the target for the home team in the 50th minute, receiving the ball from outside the penalty area and then drilling in a low shot past Loris Karius.