Full-back Stuart Spruce appears to have lost his fight to join the Bulls' bid for successive Challenge Cup crowns at Twickenham on Saturday.

The former Great Britain star was part of the 19-man squad which arrived at their training base in Slough last night.

But the T&A understands that following scans on his damaged shoulder he has been ruled out of Brian Noble's plans and will not be named in the side when the players assemble for training today.

Noble will keep his selection under wraps until just before kick-off but the loss of the experienced Spruce is undoubtedly a setback as he bids to mastermind victory over the world club champions.

Aussie Challenge Cup specialist Michael Withers is the favourite to take over as the last line of defence after impressing on several previous appearances there.

But first he must receive clearance from medical staff after breaking the major bone in a hand less than three weeks ago.

Provided Withers does come through, it would leave young back-rower Lee Radford as the most likely man to sit the game out alongside Spruce.

Noble meanwhile will be concentrating largely on tactics with the players today.

"After the schedule they have had the last thing they want is hours of physical work," he said.

"The games have come thick and fast in the last couple of weeks but it's important we iron out one or two things prior to Saturday.

"I know there have been some comments about our tactical kicking recently and we will certainly be looking at that. But I'm confident we have the players in the squad to do the job."

The Bulls party will visit Twickenham tomorrow morning to have a look at the surroundings which will be new to the majority of the team.

"Those lads involved with the England side in the World Cup will know all about it but it gives us a good chance to acclimatise as a group," said Noble. "There will obviously be nerves on the day but the visit should help on that front too."