The Dutchman suffered the setback during the first half of United's 1-0 win over Birmingham at St Andrews which lifted them back into second place in the Barclays Premier League.

Van Der Sar continued between the posts until half-time, but was then replaced for the second 45 minutes by Tomasz Kuszczak.

His injury took the shine off a fortuitous single-goal victory courtesy of Cristiano Ronaldo's 51st-minute strike.

United boss Sir Alex Ferguson said: "Van Der Sar has damaged his toe. To what extent, we are not sure. We will send him for a scan but he will definitely be out on Tuesday.

"It is a worry to lose a man of his experience, but Tomasz is very able and we are pleased we've got someone as good as him."

Van Der Sar and his replacement were kept busy by a Birmingham side showing plenty of skill and commitment and Ferguson admitted: "On reflection, that is the best side we have played this season.

"In the first half we were lucky, although we did carve out a few chances of our own. I couldn't wait to get in to half-time.

"Birmingham were very athletic, very aggressive, very quick about the pitch and even at 1-0 I was still praying we would get through the match.

"We had opportunities but Birmingham, in the first half, had even better ones."

Ferguson was full of praise for Ronaldo, who scored his first league goal of the campaign in what was his 100th Premier League start.

He said: "Ronaldo was sensational again today. The boy is so talented. His capabilities are unending.

"The goal might have come from a mistake but his composure was excellent."

Ferguson is optimistic midfielder Owen Hargreaves will be fit to face Roma after recovering from a thigh problem.

He said: "Owen trained yesterday and did well. We will see what he is like tomorrow but we are very hopeful he will be okay."

Birmingham boss Steve Bruce was left to rue his side's failure to convert any of their first-half chances but was proud of his team's performance.

The former United captain said: "We gave a terrific performance, especially in the first half, and we needed to take one of those chances. To create four or five in the first half against the champions was terrific.

"The sad thing for me is we made a horrible mistake for their goal and got punished. To lose like that is cruel.

"It was and individual error but I was proud of the way we played and we could have taken something from the game."