Former England, Tottenham and Hull midfielder Ryan Mason has been forced to retire from football at just 26 due to a fractured skull sustained last year.
Mason, needed surgery after clashing heads with Chelsea's Gary Cahill while playing for Hull in January 2017, was advised by doctors not to play again.
"Ryan has sought the guidance of numerous world renowned neurologists and neuro surgeons who have all advised that a return to competitive football is not advised," read a Hull City statement.
Hull signed Mason, who won one cap for England in 2015, for a club record fee of around £13m in 2016.
Yet his last appearance came over a year ago when he clashed heads with Cahill at Stamford Bridge and suffered bleeding on the brain. Mason required eight minutes of treatment on the pitch before being given oxygen as he was stretchered off.
He had surgery at St Mary's Hospital in London during which doctors inserted 14 metal plates and 42 staples into his skull.
"I have worked tirelessly in order to be able to return to the pitch," said Mason.
"Unfortunately, having taken expert medical advice I now have no option but to retire due to the risks involved given the nature of my injury.
"I am and always will be eternally grateful for the incredible network of people around me who have helped me to recover from what was a life-threatening injury in January 2017."
Mason came through the ranks at Spurs and played 70 games for the club before moving to Hull. He was injured in just his 20th appearance for the Tigers.