JAMES Brown has shaken Worcester Rugby Club with the news that he could be out of action until Christmas.

The fly-half has been struggling with a disc problem in his back since his summer arrival and will go under the knife tomorrow.

The club will know more after the surgery but initial fears are he could be missing from first team duty until late December.

Brown's absence will put more pressure on Craig Chalmers to last the pace and director of rugby John Brain admitted Brown's operation was a blow.

"It is a blow for us but we've just got to get on with things," he said. "We cannot really speculate on the time scale of James' absence. We will know a lot more after the surgery, but at the moment I think the worst case scenario is Christmas at the latest."

Brown started Worcester's opening league match at Coventry but has struggled since with injury.

"It's a problem where the disc is coming into contact with a nerve and causing him pain," added Brain.

"That pain is preventing him from playing so we thought it was the right time for him to cure the problem. We will know the timescale we are dealing with after the surgery and if it is short term then we will not look in the market place to bring someone in. We are very happy obviously with Craig Chalmers and Jon Higgins has been impressive when he has come into the team. We are confident in them both."

Chalmers continues at fly half on Saturday as Worcester continue their promotion bid at London Welsh. Chris Garrard returns in place of Craig Hudson on the wing while David Officer comes in for Gary Trueman at centre.

In the pack, Worcester start with the same front five but bring Christian Evans into the back row at blindside with Richard Bates reverting to number eight. Jim Jenner takes his place on the bench with lock Craig Gillies who has recovered from an ankle injury. Neil Lyman, however, drops out because of a hamstring niggle.

Worcester: Roke; Ezulike, Officer, Hinshelwood, Garrard; Chalmers, Swanepoel; Windo, Hall, Olver, Gabey, Morgan, Evans, Nias, Bates. Reps: Trueman, Higgins, O'Reilly, Pearson, Davis, Gillies, Jenner.

* Worcester's academy stars are in action against Leeds at Sixways on Saturday. The under 21s will be on the stadium pitch while the under 19s play on pitch three -- both kick off at 3pm.

There will be more action at Sixways on Monday when Harlequins visit for a second team clash, kick-off 7.30pm.