Will Fraser will not play in this Sunday's Heineken Cup semi-final against Toulon and could miss the rest of the season due to a shoulder injury.

The flanker was forced off after 16 minutes against Gloucester on Saturday and had a scan that night to determine the extent of the injury.

Sarries director of rugby Mark McCall told the Times Series today that while the results of the scan are not yet clear, Fraser will not be available to play against Toulon at Twickenham.

"Will's got an injury to his shoulder and he won't be available to play this weekend," McCall said.

"It's a very unusual injury, I can't be very specific on it because we're still exploring exactly what the problem is.

"We need to take advice from some experts before we decide how to handle it and before we know how long he will be out for or whether he'll be out for the rest of the season."

The news will come as a huge blow for Saracens who will now have to decide whether Jacques Burger, who has only recently returned from a 15-month knee injury, is ready to step in for such a crucial game.

McCall said his biggest disappointment however is for Fraser himself.

"It's a blow for Will himself more than anything," McCall continued.

"Because he's had a great season and he's played an important part in getting us to the semi-finals of the competition. 

"So I'm really disappointed for Will but we've got a number of back-row forwards who are good players and who we trust."

Fraser was called up to the senior England squad for the first time during the Six Nations in February and was on course to be involved in this summer's tour to Argentina.