Former Celtic and Manchester United midfielder Liam Miller has died at the age of 36.
Miller, who won 21 caps for the Republic of Ireland between 2004 and 2009, had been suffering from cancer.
Miller started his career at Celtic in 2000 before moving to Old Trafford four years later, also playing for Leeds, Sunderland, QPR and Hibernian.
Celtic said they were "deeply saddened", adding their "thoughts are with his family and friends".
BBC Scotland pundit Tam McManus tweeted: "I'm afraid it is true that Liam Miller has sadly passed away today. Thoughts are with all his family and friends at this horrendous time. So sad."
Miller ended his career in the United States in 2016, having also played for three clubs in Australia and his hometown club Cork City before retiring.
'A gentleman, a friend, a great player'
McManus added that "the esteem Miller was held in by supporters of every club he either played for or against" showed through in the tributes paid to him on Friday.
He himself described Miller as "a wonderfully talented player but more importantly a lovely, humble person who never changed despite the wealth and success".
Stiliyan Petrov, who played with Miller at Celtic, said he was "deeply saddened to hear of the passing of my friend and old team-mate Liam Miller".
Petrov, 38 and now retired, returned to football in 2016 having recovered from acute leukaemia, four years after being diagnosed with the disease.
He added: "My thoughts and prayers are with his family and friends. RIP my friend."
Chris Sutton, who also played with Miller at Celtic, tweeted: "Terribly sad news about Liam Miller. Taken too young. Thoughts go out to his family."
Former Manchester United midfielder David Beckham said "Our thoughts are with Liam's family. Rest In Peace."
Hibs said they were "incredibly saddened" by news of Miller's death, while Sunderland also paid tribute to their former player.
"We are saddened to hear this evening that former Sunderland midfielder Liam Miller has passed away. Our thoughts are with his family and friends at this time," the club tweeted.
Kevin Kilbane, who was Miller's team-mate with the Republic of Ireland, tweeted: "Sad hearing the awful news that Liam Miller has passed away this evening, taken far too soon by a terrible disease. Proud to have shared a dressing room with him over the years."
Kevin Doyle, who also played with Miller for the Republic of Ireland, tweeted: "Extremely sad news. Rest in peace Liam Miller, a gentleman."
Danny Higginbotham, a former Sunderland team-mate, described Miller as a "great player but more importantly a fantastic person".
"So sad," he added. "Devastating news. My thoughts are with his family."
Manchester United said the club were "deeply saddened to learn of the tragic death" of Miller and they extended their "condolences to his loved ones at this extremely difficult time".
QPR and Leeds also said they were "deeply saddened", adding: "Our thoughts are with his family and friends."
Australian club Perth Glory said "everyone associated" with them was "absolutely devastated by the tragic news".
Mark Burchill, who played with Miller at Celtic, tweeted: "Can't believe my old team-mate Liam Miller has passed away today. Taken far too soon. Horrific news. Thoughts and prayers with his family at this time."