Sunderland midfielder David Vaughan is expected to miss the beginning of the new Premier League season following a hernia operation.
The 29-year-old suffered a setback during the club's pre-season tour in South Korea after having surgery on a hernia problem in the summer.
"David had a hernia operation and didn't feel too bad," the Shields Gazette quotes manager Martin O'Neill as saying.
"He had a few injections to sort everything out, did a bit of training on the day after our first game in Korea and felt great, but then the following day he didn't feel so good.
"The medical staff are investigating and they think that they should be able to sort it out. But it's a setback because he could be out for a few weeks again and pre-season is really important."
Sunderland's first match in the new 2012-13 season is against Arsenal on August 18.
