Besiktas say defender Fabrice N'Sakala is "doing much better" after collapsing during Saturday's Turkish Super Lig match with Gaziantep.
N'Sakala, 31, fell to the ground in the 70th minute and was taken to hospital, but the cause is not yet known.
Besiktas said their left-back was conscious, and the decision was precautionary.
The match, in which on-loan Chelsea striker Michy Batshuayi made his debut for Besiktas, ended 0-0.
"The Congolese international left-back was taken to the hospital immediately," his club said in a statement on Sunday. "The early reports have shown that he is in better condition and doing quite well.
"Besiktas have thanked those football lovers who have shown concern."
The incident comes two months after Denmark midfielder Christian Eriksen suffered a cardiac arrest on the pitch during a Euro 2020 group-stage match against Finland in Copenhagen.
- "My body's tired... but my mind is racing": Why are thousands of young people struggling to sleep?
- The Merthyr Mermaid: Follow Cath Pendleton as she prepares to swim a mile in Antartica