Best has been diagnosed with a left hip labrum tear, an injury picked up in pre-season training, and he will go under the knife next week to cure the problem.
Brian Downey, Director of Sports Medicine at Sixways, said: "Lee has worked hard but he has not responded to conservative management and the only option now open to him to correct the problem is surgery.
"We would expect him to be out for between three to four months and we anticipate a return to action in early January."
Best, 28, made 18 appearances for Warriors last season after a move from Bath Rugby, scoring two tries including a memorable effort in the Guinness Premiership derby clash with Gloucester at Kingsholm.
Director of Rugby Mike Ruddock spoke of his disappointment at the injury on the eve of the season but has backed Best to make a full recovery.
"This is a blow for Lee and a blow for the club as we're about to embark on a demanding new campaign," said Ruddock.
"Lee had worked hard all pre-season to get into good shape in terms of his conditioning and skills and we would have liked to have had the opportunity to see him on the field from day one.
"This injury has prevented that and despite some excellent medical treatment on the injury during the last few weeks is has become obvious that an operation is now required.
"He has had a number of injuries in the past and has always comeback better than ever and we anticipate that will happen again in this case.
"We wish Lee a swift return to full fitness and we are fortunate that we have some great strength in depth with the return from injury of young Chris Pennell and players like Shane Drahm and Thinus Delport who can play in that position."