SAM Allardyce fears Wanderers could be out-muscled, never mind outclassed, at Old Trafford tomorrow, if they don't have the stomach for a fight.

The Bolton boss is worried the team he built into one of the most formidable forces in the Premiership has developed a vulnerable streak that could be ruthlessly exposed by Manchester United.

"Yes, we've gone soft," Allardyce admitted on the eve of a derby duel that could have a major bearing on the fortunes of the two Greater Manchester rivals.

It was a brutal but honest analysis of performances that have left Wanderers - serious Champions League contenders at the turn of the year - facing a desperate struggle to qualify for the UEFA Cup.

And, at the same time, he poured scorn on anyone who under-estimates the physical attributes that have helped United emerge as red-hot title favourites.

With Chelsea trailing by only six points and United still having to go to Stamford Bridge, Allardyce is not yet prepared to acknowledge them as champions-elect, but, in Sir Alex Ferguson's side, he sees Premiership heavyweights capable of landing knockout blows against any team that is not prepared to get physical.

He said: "If you start with the goalkeeper, who is 6ft 4ins, Gary Neville, who is not the biggest but can mix it with the best in the world, Ferdinand, Vidic, Heinze, Carrick, O'Shea and Ronaldo - who, when you get close up to him, is huge - the physical size and strength of Manchester United is equal to anybody else in the Premiership, and the skill levels are very good as well."

Wanderers have been encouraged by the manpower crisis that has robbed Ferguson of so many key players but one clean sheet in their last eight league and cup games and 18 goals conceded, are statistics that particularly alarm the manager.

"The biggest part of the game is earning the right to play," he said. "You've got to stop the opposition from doing what they want to do, first and then take advantage of what you've got to break down the opposition, and we've lost a little bit of that.