Ospreys wing Dafydd Howells is likely to be out for the rest of the season with ankle ligament damage.
The 19-year-old will not need surgery but is out for at least 10 weeks after being forced off in the early stages of the Pro12 game against Glasgow.
Howells won two caps for Wales on tour to Japan in 2013.
"It is quite substantial ligament damage, but the good news is that he doesn't require surgery," Ospreys' Chris Towers said.
Fly-half Sam Davies is undergoing concussion protocols after going off in last Friday's draw against Leinster, but the region hope he'll be fit to face Munster.