Fergus McFadden injured his hamstring in the process of scoring Leinster's third try against the Scarlets and will play no part in this weekend's Pro14 derby trip to Connacht.
The wing crashed over on the stroke of half-time at the Aviva Stadium on Saturday, giving his side a 24-9 advantage in the Champions Cup semi-final they never looked remotely like relinquishing.
He took a heavy knock from Steff Evans as he touched down however and was replaced at the break by Jordan Larmour.
After the game, Leo Cullen said: "It looks like it's his hamstring. We'll see how he is. I'm not 100% sure. We'll get him a scan early in the week and get him an update then."
Leinster confirmed that assessment on Monday, while also revealing that Luke McGrath (ankle) and Rhys (hamstring) will be further looked at during the week.
Robbie Henshaw made a hugely impressive return to action at the Aviva and he has come through his first taste of action since the Six Nations unscathed.
Henshaw had been on the sidelines since damaging his shoulder against Italy.
Flanker Sean O'Brien's season is over after he underwent shoulder surgery last Friday.
