British and Irish Lions selection Dan Biggar will have tests on an injured ankle after limping off in Ospreys' 40-17 defeat by Scarlets.
Biggar started with a bandaged foot and went off early in the second half.
Ospreys go to Munster in the Pro12 semi-final on 20 May and the Lions fly to New Zealand nine days later.
"We will assess him over the next 24 hours, he is just adding to our list of casualties," said Ospreys head coach Steve Tandy.
"It was something to do with his ankle, we have just got to dig into it in a bit more detail."
Biggar was one of 12 Wales players named in Warren Gatland's tour party.
Ospreys went into the game with Scarlets with 15 players on their injury list, but hope to have club captain Alun Wyn Jones back for the semi-final.
The record defeat against their west Wales rivals was their fourth loss in their past five Pro12 games.
As well as Jones, Tandy expects fly-half Sam Davies, Ashley Beck and Brian Mujati to be fit again for the semi-final at Thomond Park in Limerick.
Tandy said he was proud of his team's performance over the season, claiming a Pro12 play-off place and a place in the European Champions Cup.
Asked if Ospreys would throw the kitchen sink at Munster, he replied they would have to, adding: "But we'll have to find a kitchen sink first.
"We know how difficult they are to play, powerful and a passionate crowd.
"Looking at it, everyone apart from the people in our changing room don't think we can do it so we have something to prove.
"It's a semi-final and we're pretty excited.
"We're disappointed about today but there's nothing we can do about it. But over a 22 game season, and where we came from last year, we're pretty pleased with it."