Manchester United striker Ruud van Nistelrooy will undergo a scan later on Friday as concern over his calf injury deepens at Old Trafford.

The Dutchman, United's top scorer with 12 goals this season, has missed the last four matches with the problem.

"Ruud isn't any better and we are having to reassess what we are going to do about it," United manager Alex Ferguson told the Manchester Evening News.

"The danger is with calf injuries they start to move down to the Achilles. That is our concern.

"He will go for a scan today and then we will wait and see what to do next."

Van Nistelrooy last played in United's 3-0 victory at West Bromwich Albion three weeks ago.