Stoke defender Andy Wilkinson has retired from football at the age of 31 after suffering concussion in a match last February.
"Over a year on from the injury there are still a lot of things going on with my brain, my vision, my neck - all sorts of different symptoms," he said.
"The risk [of returning to the game] is far too high."
The full-back was hit by a volley at close range during an FA Cup tie against Blackburn.
"As time went on I suffered with other things - vertigo, nausea, balance problems," Wilkinson told Sky Sports News. "Then problems mentally with anger, feeling a bit depressed."
Former Stoke manager Tony Pulis paid tribute to Wilkinson as "an honest hard-working person".
He added: "He gave just about everything, and I mean everything, in training, in games.
"Whatever you asked him to do, he never ever moaned or groaned. He would always do everything to the best of his ability."
Wilkinson made 194 senior appearances for the Potters, including playing in the 2011 FA Cup final defeat to Manchester City.