Harper sustained ligament damage after landing on his left shoulder following a challenge by Jermaine Beckford during Saturday’s 1-0 win at Everton.

Newcastle described Wednesday’s operation as “successful” but the prognosis means Harper, 35, is unlikely to figure again until mid-December.

Tim Krul, who took over at Goodison Park, is set to continue in the role.

The 22-year-old Dutch keeper started Wednesday’s 4-3 Carling Cup victory at Chelsea, with 20-year-old Swedish netminder Ole Soderberg named on the bench.

Newcastle manager Chris Hughton described the challenge by Beckford, who was booked for the 35th-minute incident, as one “that didn’t need to have been made”.

“Steve Harper was always getting there first,” Hughton added.

Harper has been with Newcastle for 16 seasons, spending 12 years as reserve to Shay Given.

After Given joined Manchester City in January 2009, Harper took over as Newcastle’s first-choice keeper.