Cian Healy suffered an ankle injury in today's warm-up match against Western Force and could be a doubt for the Tests against Australia.
The Irishman went down injured during the Lions' match against Western Force and had to be carried off. Should the 25-year-old be ruled out, it would be a huge blow for the Lions.
Early indications are that the prop has not broken anything but his ankle has suffered a serious sprain.
The player, who was accused of biting an opponent earlier in the match, is expected to undergo an x-ray.
Jonathan Sexton scored the Lions' first try on Australian soil of this tour as Warren Gatland's side got off to a strong start in their warm-up game.
Gatland said before the match he was disappointed with Michael Foley's decision to field a weakened side and the gulf in quality was evident as the Lions dominated early proceedings.
Leigh Halfpenny opened the scoring with a penalty after just three minutes and Sexton extended the lead when he touched down seven minutes later. The Ireland fly-half, who faces a showdown with Owen Farrell for the Test jersey, split the home-side's defence with a show and-go and finished easily under the posts.
Force captain Matt Hodgson said before the game his side wanted to hurt the Lions but it was the tourists who courted early controversy when Healy was accused of biting Bret Sheehan. However, the Television Match Official ruled there was no case to answer.
Force reduced the score with a penalty before captain Brian O'Driscoll touched down in the left-hand corner for the Lions second try, which was converted to make it 17-3, shortly after half an hour. The Lions then suffered the blow of Healy being carried off.
Sam Warburton was again ruled out with injury but the tour skipper delivered a boost to his team-mates by completing his first full training session ahead of kick-off. The Wales and Cardiff Blues flanker did not feature in Saturday's 59-8 victory over the Barbarians but will now have his eye on a Lions debut against the Queensland Reds on Saturday.
The Reds will announce their team to face the Lions tomorrow and, although key players such as Will Genia are unavailable through international commitments, head coach Ewen McKenzie is expected to name his strongest side possible.