England international Matt Mullan faces three months out of action after dislocating his shoulder in training.
The 23-year-old Worcester prop was recently named in the England Saxons elite player squad for 2010/2011. He made his senior international debut as a replacement against Italy during last season's RBS 6 Nations Championship.
Mullan will now undergo surgery and he is unlikely to play again before November.
Worcester head coach Richard Hill said: "We are bitterly disappointed for Matt after he was injured in what was a freak accident during training.
"The injury was not to the shoulder that ruled him out towards the end of last season, and we had hoped it would not require surgical intervention.
"It is a double blow, as I had talked to Matt about the vice-captaincy, but clearly he will now miss the early part of the season which is a crucial time for the team to get up and running."
Worcester, relegated from the Premiership last term, launch their Championship campaign at the end of August.