Leinster flanker Sean O'Brien will not return from a hip problem for the Blues trip to the Scarlets on Friday.
O'Brien has not played for Leinster since their Champions Cup win over Exeter in December, and while Ireland coach Joe Schmidt had initially hoped that the backrower could have played some part against Wales on Saturday, it now appears that he will not play in Leinster's trip to Llanelli this weekend.
"Seanie's made good progress," Leinster backs coach Girvan Dempsey told RTÉ News.
"We'll assess how he goes during the week but he upped his running volume last week and he's making strides towards a return to play, which is great news for us.
"All I can say at this moment in time is he's upped his volume last week. He'll do more running today, if he comes through that then he'll progress it tomorrow and we're fortunate that it's a long week into Saturday.
"It's going to be very optimistic that he'll be involved, if not this week, then definitely in our return game post the break. But I'd be very hopeful."
Elsewhere Ireland teammate Garry Ringrose made a successful return from ankle surgery last Friday as Leinster ran in ten tries in a 64-7 Guinness PRO14 win over the Southern Kings at the RDS.
It was Ringrose's first start since Leinster's win over Ulster last month as the 23-year-old looks to work his way back into the Ireland squad ahead of next weekend's visit of Scotland.
