Foster has lost his place in the United team Edwin van der Sar after failing to impress while the Dutchman has been out with an injury.
The Scot told the News of the World: “Ben was always going to lose his place when Edwin Van der Sar came back.
“You don’t dismiss the quality and experience of Van der Sar. You couldn’t even say he is declining – he is at his peak. He is phenomenal. He really is top dog.
“He is in training every day. He doesn’t miss a session. Plus he has that calmness about him. He never gets excited about what is happening round about him. There are not many in England you can compare him with.
“The future belongs to Ben of course. Tomasz Kuszczak is a good keeper too so we are quite strong. But Ben will not be allowed out on loan in January. No way.”
