Wales centre Cory Allen could be ruled out of the remainder of the Six Nations after suffering an ankle injury on Saturday.
Allen was carried off on a stretcher early in the second half of Cardiff Blues' 14-13 defeat to Leinster at the Arms Park.
Cardiff said his condition would be assessed on Sunday.
The injury, should it prove as serious as it appeared, will further limit Wales coach Warren Gatland's midfield options and comes as another blow to the four-cap centre who was ruled out of the World Cup after one game.
Leinster briefly went top of the Guinness PRO12 before Connacht's win over Zebre in Italy saw them claim first place.
Victory in the Welsh capital came thanks to a performance in which Isa Nacewa scored the visitors' only try, but Leinster had to withstand a late Cardiff onslaught after Josh Navidi crossed.
Cardiff welcomed back five Wales internationals including Alex Cuthbert and half-backs Lloyd Williams and Gareth Anscombe. Anscombe opened the scoring after just four minutes with a penalty from Manoa Vosawai's break.
Leinster started with six of the Ireland squad as well as a return from injury for Cian Healy.
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