George Baldock, once a Sheffield United defender, passed away at the age of 31.
The England-born Greece player was discovered dead in his home swimming pool in Glyfada, southern Athens.
According to preliminary autopsy findings, he drowned, and police sources indicate there is no evidence of foul play.
Police tried to revive Baldock on the scene, but he was unable to be revived, and health care units verified his death, according to Reuters.
Baldock moved to Greek club Panathinaikos in June after seven years with the Blades.