A minute's silence was observed before Thursday's Nations League game between England and Greece in memory of George Baldock following the death of the Greek international
Players for both teams wore black armbands while Greek players held up a Greece shirt with Baldock's name and number on ahead of kick-off.
Baldock won 12 caps with Greece, with his international debut coming in February 2022.
"UEFA would like to send its condolences to the family of George Baldock, the Hellenic Football Federation (HFF) and Panathinaikos FC following the Greek international's sudden and untimely death," European football's governing body said in a statement announcing the tribute.
Police said Baldock's body was found late Wednesday in his swimming pool in the southern suburb of Glyfada. The cause of death was not immediately clear.
Police spokeswoman Konstantina Dimoglidou said there is no initial indication the death was suspicious.
She told The Associated Press on Thursday that the coroner who examined the body "informed us that there is no evidence of a criminal act."
She added: "The house too was searched by the criminal investigations directorate. It doesn't seem that a criminal act took place but the investigation is continuing for any eventuality."
ERT television said the coroner determined drowning as the cause of death, but Dimoglidou was not immediately able to confirm that.
The cause of death remained unknown. The time of death was recorded as 10 p.m. local time (7 p.m. GMT).
The football community has widely paid tribute to Baldock, including many of his former teammates. Sheffield United said he was "extremely popular" player during his seven years at the club, while Panathinaikos said "there are no words to describe" the incident.
Information from Reuters and The Associated Press and Reuters contributed to this report.