United's first choice keeper Edwin van der Sar sustained a groin injury in the FA Cup 6th round defeat against Portsmouth on Saturday and had to be replaced by Tomasz Kuszczak.
However, Kuszczak was sent off for a professional foul which led to Pompeys penalty kick winner and will now serve an automatic one game ban.
Foster has played only ninety minutes of reserve team football this season having sustained cruciate ligament damage during last summer's close season.