Leinster head coach Leo Cullen says it is a huge blow Niall Morris has been forced to retire from the sport.
Morris suffered a fracture and a dislocation of his ankle when playing for Leicester Tigers against Bath in May 2015 and was then released by the club in April.
The 28-year-old re-joined former side Leinster in July this year on a short-term deal and managed to feature in the first two of the three pre-season games.
However, the Dubliner felt a recurrence of the problem against Gloucester in August and, following a consultation with doctors, the decision has been made to hang up his boots.
Cullen admits it is hugely disappointing for both the club and player but the head coach hopes the former Ireland Under-20 international succeeds in a life away from rugby.
"We could see during our games against Ulster and Gloucester the quality that Niall can bring to a team so we are very disappointed to hear that he now won't be able to continue playing," he said.
"All the players and staff would like to congratulate Niall on what he achieved in the game and wish him the very best for what he focuses his energy on next."