The 21-year-old has made seven Posh appearances in all competitions since joining on loan until January.
"We'd love him here until beyond, never mind the end of the season and to be one of our players," said McCann.
"But Tottenham think highly of him - he's been on the bench for their first team in the Premier League."
"He's been first-class since he's come in. Not just his performances on the pitch but his whole demeanour around the building," McCann told BBC Radio Cambridgeshire.
"He's a young lad but he's come in with a 27, 28-year-old's shoulders on him. He demands of people in training, if you don't track a runner he's out of his goal shouting at you.
"It's exactly what you need from your goalkeeper. With his ability as well, you've got somebody special."