Panathinaikos and Greece international defender George Baldock was found dead in his swimming pool on Wednesday, Greek news reports said.
The 31-year-old English-born right-back died at home in the southern Athens suburb of Glyfada, state agency ANA said. Greece's Super League and several clubs expressed their condolences.
State TV ERT said the player was "at the bottom of the pool" and a bottle of alcohol was found at the scene. ANA said Baldock's wife, who is abroad, alerted the owner of the residence after unsuccessfully trying to reach the player on the phone.
Police cars and an ambulance were outside the building and a coroner was called to examine the body, ERT said. Baldock had joined Panathinaikos in May after a seven-year spell with Sheffield United, relegated from the English Premier League to the Championship last season.