BLACKBURN Rovers defender Ryan Nelsen could be out of action until Christmas after undergoing surgery to cure a hamstring injury.

The New Zealand international flew to Finland earlier this week to see Professor Sakari Orava, one of the world's leading experts in sports muscle injuries.

And while the operation was hailed as a success, the bad news for Rovers boss Mark Hughes is Nelsen's rehabilitation could take up to four months.

"Ryan had his operation yesterday and it went well," said Hughes.

"The surgeon was very happy with what he found when he went in, he's repaired what he had to repair, so we're hopeful we'll get him back around Christmas time.

"It's unfortunate, but it needed to be done, and when he returns he will be like a new player for us.

"We had the best guy in the world performing the operation. He saw the problem, rectified it, and was very happy with the way it went.

"Hopefully, Ryan will recover quickly."

Hughes has moved quickly to cover for Nelsen's absence by signing former Rovers defender Stephane Henchoz, although the 32-year-old is still some way short of match fitness.

Henchoz, who spent two seasons at Ewood Park between 1997-99 after a £3million move from Hamburg, has rejoined the club until the end of the season, but his recent lack of match action means he won't be in a position to compete for a first team place for some time yet.

"He needs a number of weeks," said Hughes. "But given the situation we find ourselves in with Ryan, I thought we couldn't pass up the opportunity to bring in a player of Stephane's experience and ability."

One piece of good news from the treatment room is midfielder Steven Reid has a chance of playing in tomorrow night's UEFA Cup tie with Salzburg.

eid missed Saturday's goalless draw at Sheffield United with a nagging back injury, but trained without problems yesterday.

"Steven has trained so hopefully he won't get a reaction and he should be available for selection," said Hughes.

One man who definitely won't feature in Austria, however, is striker Jason Roberts after Hughes confirmed he will be missing for several weeks as a result of the groin injury he sustained in training last Friday.

"Jason will be missing for two to three weeks," added Hughes. "It's his kicking leg so obviously it's important we don't rush him back too quickly."