The Coventry City midfielder limped off in his reserve-team comeback against Notts County's second team last night and the diagnosis is that his knee requires immediate attention.
McAllister injured his knee in December and underwent a cartilage operation, but the new damage is much worse. He now faces eight months out of the game and will undergo surgery within a week.
The injury news is a big blow for Scotland and a personal nightmare for McAllister, who led his country to France but may now never appear on the ultimate stage. He was in the squad in 1990 but was an unused substitute.
The Sheffield United chairman, Mike McDonald, announced his intention to resign yesterday after a protest campaign from supporters in response to the surprise decision of the Blades' manager, Nigel Spackman, to leave the First Division club on Monday.
"I am not here to be abused," McDonald said. "I have always said that, on the football side, once the fans don't want me, I will go. We are in the quarter-finals of the FA Cup, in the top six in the League and the fans are not happy for some reason or other. I have said all along that, if they are not happy with me, then I won't be there."
Lou Macari, tipped to become Spackman's successor, yesterday said he has had no contact with the Blades over their vacancy, but that he would jump at the chance of doing the job. The former Birmingham, Celtic and Stoke manager has been out of work since July last year after leaving Stoke.
"Obviously I am flattered that my name has been mentioned and I would love the chance to get back into management," Macari said. The Blades are due to announce their new manager today.
The Bolton Wanderers defender Mike Whitlow has been ruled out for the rest of the season with knee ligament damage. The 30-year-old left-back, a pounds 700,000 signing from Leicester City earlier this season, was carried off during a game at Barnsley on 3 January.
Everton's veteran defender Dave Watson is poised to sign a new one-year contract with the club. Claus Thomsen, the club's Danish midfielder, though, is to leave Goodison for AB Copenhagen for a fee of pounds 500,000.
The Crystal Palace forward Attilio Lombardo is set to return to first- team action next week against Chelsea. He tore a thigh muscle while training with the Italian squad in November and his comeback in December ended after 48 minutes when he was injured again.Reuse content