The Italian stopper has been in excellent form for the Black Cats of late, helping Gus Poyet’s side to turn around their early season poor form and move out of the foot of the table.
His excellent displays have alerted David Moyes, who is said to be on the lookout for a new glovesman to keep David de Gea on his toes.
Current backup man Anders Lindegaard is believed to be nearing a move away from Old Trafford in search of regular action, which would leave the Premier League champions short on challengers to the current number one.
The former Arsenal ace is seen as the ideal man to provide de Gea with competition, and could be the subject of a serious offer before the transfer window closes.
Despite Mannone having been a regular of late, Poyet could sanction a sale in order to free up space to draft in Catania keeper Mario Andujar – whom has admitted to having an interest in a move.