Ravel Morrison has returned to parent club West Ham from Cardiff City on compassionate leave.
Brighton boss Sami Hyypia is weighing up a move for former France captain Alou Diarra.
The 26-year-old has shone for the Canaries in their rise to the top flight and has become a regular in Roy Hodgson's England squad.
However, Ruddy faces a substantial period out of action after being forced off with a thigh injury eight minutes from the end of Saturday's 1-1 draw with Everton.
A post on Norwich's official Twitter account said: "City can confirm 'keeper @Johnruddy86 has a thigh injury which is being assessed, but he could be out for approximately 3 months."
The club's confirmation followed a tweet from Ruddy himself, revealing he will go under the knife this weekend.
The goalkeeper, @Johnruddy26, said: ''Just to update everyone on my injury, unfortunately I have torn my thigh will be having surgery on saturday and out for up to 3 months, :(''
It is a huge blow for in-form Norwich, who are unbeaten in their six Premier League matches heading into tonight's match at Southampton, where Mark Bunn deputised for Ruddy.