Lambert rates Guzan highly and expects him to provide a strong challenge to Given when he puts pen to paper on a new contract shortly.
"It's near," said Lambert.
"I've watched Brad and some of his games when he was in the team last year and he was excellent.
"I know he's always had that stigma of being the No.2 behind some really good goalkeepers here.
"But when you come back at the start of the season nobody knows what's going to happen and it depends on whoever does well.
"Brad played very well the time he was in and maybe he found himself a bit unlucky to be back out."