Chris Farrell is expected to miss Munster's trip to Castres on Saturday after pulling out ahead of last Sunday's win over the Top 14 champions at Thomond Park.
The Irish centre suffered a quad strain, after being named to start the Champions Cup clash.
Munster coach Johann van Graan is confident that Joey Carbey, also a late withdrawal last weekend, will be fit for selection ahead of Saturday's Champions Cup pool match at the Stade Pierre Fabre (5.30).
Meanwhile the Scarlets will be without fullback Leigh Halfpenny (HIA) - he missed last weekend - centre Kieron Fonotia (lower leg), prop Rob Evans (ankle) and flanker James Davies (toe) for their game against Ulster at the Kingspan stadium on Friday night (7.45).
Ulster have added Ian Nagle to their Champions Cup squad - the lock is on a six month loan from Leinster and having missed last weekend’s clash his return is a boost to their options in the secondrow.
