Midfielder Paddy McNair is expected to miss the first six weeks of the new season because of an injury setback, Sunderland boss Simon Grayson has confirmed.
McNair had been working his way back to fitness after rupturing a cruciate ligament in November, but Black Cats manager Grayson says he is likely to sit out the early stages of the Championship campaign.
It is understood the 22-year-old Ballyclare man required minor surgery on his knee cartilage.
The news is a blow not only to Grayson but to Northern Ireland manager Michael O'Neill whose side face crucial World Cup qualifiers against San Marino and Czech Republic in early September.
"Paddy had a little bit of a setback with his knee and has had to have a bit of a clean up in there which probably means he will miss the first six weeks of the season," Grayson told the Sunderland Echo. "So, that is a blow for us. We wish Paddy a speedy recovery."
"We like to think all the players we have on our books will be a handful for most teams in the Championship, the same goes for Paddy. You have to earn the right.
"Paddy is in good hands and will come back in a good condition. He just had a setback which can sometimes happen after a long injury.
"I have not seen him yet ... he is coming up to Scotland with us so that will be the first chance I get to catch up with and speak with him."
Last month McNair posted video of him training in Portugal in his bid to regain fitness. "Enjoying a week of hot weather training in Portugal before the start of the new season," he wrote.
McNair played nine times for Sunderland in the Premier League last season before injury struck. McNair's last appearance in the green and white of Northern Ireland came in last year's friendly against Croatia at Windsor Park.