Allardyce is in no doubt that Hexham-born Forster, 6ft 5in and still growing, is ready to challenge Shay Given - sidelined with groin trouble - and Steve Harper in the long term.
"We don't need to recall Tim Krul, because we've got Fraser - who's top drawer," Big Sam told the Sunday Sun.
"He's really shown in the reserves a lot of outstanding qualities. He's young and inexperienced but he looks a very promising young goalkeeper.
"I'd be happy to use him."