London - Munster scrum-half Tomas O'Leary could be forced out of the British and Irish Lions tour to South Africa after suffering a suspected fractured ankle in his team's 29-10 Celtic League win over the Scarlets on Friday.
O'Leary, 25, was immediately ruled out of next weekend's European Cup semi-final against Leinster.
The injury occurred in the early stages of the game at Musgrave Park when he collided with David Wallace and turned his left ankle. He had to be taken off on a stretcher.
"It's disappointing for O'Leary, poor guy," said Scarlets fly-half Stephen Jones, a fellow British Lion.
"He's been fantastic this season and I believe he's fractured his ankle and it's a sad loss."
Peter Stringer replaced O'Leary in Friday's game and he could be one potential replacement on the tour to South Africa. Other candidates could be Scotland's Mike Blair, Wales' Dwayne Peel and England's Danny Care.
Harry Ellis and Mike Phillips were already named in the squad.