Head injury forces McCormack out of derby and Scotland duty

The 26-year-old, joined on the absentee list for Scotland by James Forrest and Danny Fox, had wanted to play in United’s derby with Huddersfield Town.

However, the bang to the head that McCormack received in last week’s draw with Peterborough United – which the striker later revealed had led to him being unable to recall any of the second half – was adjudged to be so severe that he had to sit out the 2-1 defeat to the Terriers.

Warnock said: “Ross actually wanted to play against Huddersfield on Saturday, and I wanted him to play. But you can’t go against the doctor, who said it was a very serious situation.

“As much as I would have liked him out there you can’t go against medical experts. Ross couldn’t remember anything of the Peterborough game.”

Scotland assistant manager Mark McGhee believes McCormack, Southampton’s Fox and Forrest of Celtic are unlikely to be available to face Serbia a week tonight after earlier being ruled out of Friday’s encounter with Wales.

As a result, Norwich City defender Steven Whittaker has been drafted in by Gordon Strachan, who is preparing for his first competitive game as national team manager at Hampden.

Whittaker made his first appearance of 2013 on Sunday when he came on as an 89th-minute substitute against Sunderland.

“Gordon spoke to Chris Hughton and Steven and feels he has done enough to be here if he is needed,” McGhee said.

“We probably feel he hasn’t played enough games that he would be in serious contention, but I think he is one the manager feels will be here in the future.”

Fox has missed Southampton’s last two games after going off with a thigh injury in their defeat to QPR earlier this month. McGhee admitted the loss of Forrest was a “big, big blow”.

“I think the manager had hopes he would play, so that is very, very disappointing,” said McGhee.