Newcastle will be without Damien Duff for some time after the Irish winger went under the knife on Thursday.
Duff injured his knee during Saturday's draw at Arsenal and scans revealed damage to his cartilage.
The fleet-footed winger travelled to see a specialist in the capital who advised that surgery was the best course of action.
Duff's operation is believed to have passed off without a hitch and he will soon begin his rehabilitation programme.
The initial forecast stated Duff would be out of action for a month, but the club will know more when he is assessed by his surgeon.
Keeper Steve Harper is set to have surgery on his groin next week, with the return of Shay Given allowing the club to send their number two for an operation.
"Now that Shay Given is back in the swing of things this will allow Steve Harper to have a minor groin operation sooner rather than later, maybe even next week," said Magpies chief Glenn Roeder.