Crockett lifted the Amlin Challenge Cup with Bath in 2008 and made over 30 European appearances but will miss Worcester's return to the competition this year.
"We are all hugely disappointed for Crocks as he had just worked himself into some good form and had featured in the Premiership for us this season and played in the recent encounters," said director of rugby Richard Hill.
"We now wish him well with his recovery under the guidance of the medical and rehabilitation staff at Sixways.
"It is a blow for us, but we are lucky to have good depth in that area of the squad.
"Dale Rasmussen and Alex Grove have performed strongly for us in the league and we also have Sione Tu'ipulotu, Chris Pennell and Tom Arscott who can play in that position.
Worcester kick off their 2011/12 European campaign by hosting last season's beaten finalists, Stade Francais at Sixways on Thursday November 10.