Former Sheffield United defender George Baldock drowned while swimming in the pool at his home in Athens, a family statement has said.
Greek police earlier confirmed there was no evidence that criminal activity caused the death of the 31-year-old Greece international, who signed for Athens club Panathinaikos in the summer.
"We are heartbroken with the sudden passing of our beloved George. We can confirm that a post-mortem examination has found that George tragically drowned whilst swimming in the pool at his home in Glyfada, Athens," a statement from Baldock's family read.
"George, you were the most special father, fiance, son, brother, uncle, friend, team-mate and person. Your enthusiasm and infectious personality brought so much love to those that were fortunate enough to know you and those that adored you from the stands.
"We will forever cherish the special memories we have of you and you will continue to live on in your beautiful son. You were due to fly home today for us to celebrate his first birthday together, but instead we mourn your loss.
"As a family it has been incredibly touching, but equally so very difficult to read the huge number of tributes written by those that knew George and from those whose life he touched.
"It was impossible not to love him. We ask that you please continue to respect our privacy at this devastating time as we begin to process our grief."
Greece international Baldock signed for Panathinaikos this summer after a seven-year spell at Bramall Lane, making his debut in August.
The Greek club posted a tribute on Instagram, writing: "We are shocked by the loss of our George. Panathinaikos' family mourns his unexpected loss. We stand with the family and relatives of George Baldock."
There was a period of silence before Thursday night's Nations League match between England and Greece at Wembley, with Baldock's picture shown on the big screens.
Players of both sides also wore black armbands and the Greece team held up his shirt before kick-off.
A Super League Greece statement released earlier read: "The entire Super League football family expresses its deep sorrow for the untimely loss of Panathinaikos and our national team footballer, George Baldock, and extends its deepest condolences to his family and loved ones."
A Greek Football Federation statement read: "With deep sadness and pain, the National Team and the Hellenic Football Federation say goodbye to George Baldock.
"There are no words to describe the human pain caused by the news of the untimely loss of one of our young people. The moment calls for silence. Condolences to his family. Condolences from his second family. Goodbye."
England international and former Sheffield United player Harry Maguire posted "RIP" and a heartbreak emoji alongside an image of Baldock on Instagram.
Northampton, where Baldock had a loan spell in 2011, wrote on X: "We are deeply saddened to learn of the passing of former loanee George Baldock at the tragically young age of 31.
"George made five appearances in 2011 before playing for Oxford United and Sheffield United. Sending our sincerest condolences to George's family and friends."
Baldock was born in England and started his professional career at MK Dons, where he spent eight years.
After several loan moves to clubs including Tamworth, Oxford United and Northampton, the defender made a permanent move to Sheffield United in 2017.
He made more than 200 appearances for the Blades - including 83 outings in the Premier League, where he scored two goals and registered six assists - before joining Greek side Panathinaikos this summer.
Baldock, capped by the Greek national side on 12 occasions, made four appearances this season across all competitions.