Former Aston Villa and Cardiff midfielder Peter Whittingham died on Thursday at the age of 35 following an accidental fall.
Whittingham had been in hospital since suffering head injuries at a pub in the seaside town of Barry on 7 March.
He reportedly fell down a flight of stairs after watching England play Wales in the Six Nations tournament.
In a statement on their website, Cardiff said: "It is with an immeasurable amount of sorrow that we must inform supporters that Peter Whittingham has passed away at the age of 35. We are heartbroken.
"The news of Peter's sudden and untimely passing has shaken us to our very foundation."
Whittingham, a former England Under-21 international, started his career at Villa and won the FA Youth Cup with them in 2002.
He played 66 games for Villa and had loan spells at Burnley and Derby before joining Cardiff in 2007.
Whittingham helped Cardiff reach the 2008 FA Cup final, which they lost 1-0 to Portsmouth, and the 2012 League Cup final, where they were beaten on penalties by Liverpool.
He was in the side who won the Championship in 2013, taking Cardiff back to the top-flight for the first time since relegation from the old Division One in 1962.
He moved to Blackburn after 450 appearances in a decade with Cardiff and finished his career at Ewood Park in 2018.
"Our love goes out to his wife Amanda, their young son and family. They are at the forefront of our thoughts and, on their behalf, we ask for their privacy to be respected at this unfathomably cruel and difficult time," the statement said.
"First and foremost, Peter was a family man - and somebody who could light up a room with his sense of humour, warmth and personality. Then, as a professional footballer - as a Bluebird - he excelled with talent, ease, grace and humility. Nobody did it better.
"The loss of Peter will be painfully felt by our city, supporters and indeed all who ever had the pleasure of knowing him. We love you Pete and your memory will eternally stay with us."