Footballer Bekir İrtegün was arrested in Istanbul on Friday as part of a probe into the Fetullah Terrorist Organization (FETO), according to a police source.
İrtegün played for popular Turkish clubs -- Gaziantepspor, Fenerbahçe and Başakşehir -- in the recent past.
His passport was also seized just two weeks before he was due to go abroad.
İrtegün was released from his former club Medipol Başakşehir on July 10, despite having another year in his contract.
FETO and its U.S.-based leader Fetullah Gülen orchestrated the defeated coup of July 15, 2016, which left 250 people martyred and some 2,200 injured.
Turkey accuses FETO of a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police, and judiciary.
