Panathinaikos and Greece international 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.
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.
Of Greek origin through his father, he was called to the Greek national team in 2022.
He had 12 caps, but had not been selected for the team's Nations League match against England at Wembley on Thursday owing to injury, ERT said.
Both the Greece team's official website and his club's social media sites on X, formerly Twitter, and Facebook, were blackened in tribute to the player.
