Worcester Warriors flanker Jake Abbott is set to be out for a lengthy spell after rupturing his anterior cruciate knee ligament.
The 25-year-old sustained the injury in last week's LV= Cup match against Sale Sharks.
Abbott has been an essential player under new boss Dean Ryan since he took over at the start of the season, featuring in every match so far.
The openside will undergo surgery this week, with Worcester currently not offering a firmer indication of when he will be able to return.
"Jake's loss leaves a big hole. We'll miss his relentless energy," said Ryan.
"However, I have no doubt that Jake will approach this challenge with the same determination and commitment that he always displays around the club."
Worcester return to Aviva Premiership action against Sale on Friday, currently sitting nine points adrift at the bottom of the league.