Wales confronted a mounting World Cup injury crisis Monday with try hero Cory Allen expected to exit the tournament.
Coach Warren Gatland said Allen, who got three of the eight tries in Sunday's 54-9 victory over Uruguay, suffered a "significant" hamstring tear.
He was to undergo a scan on Monday.
With Wales to play England in one of the crunch matches of Pool A on Saturday, there are doubts about front row pair Paul James and Samson Lee, Aaron Jarvis has a damaged rib while full back Liam Williams left Sunday's game with a thigh injury.
Gatland has already had to patch up the team after star full-back Leigh Halfpenny and first-choice backs Rhys Webb and Jonathan Davies dropped out before the tournament started.