Charlie Wyke has been ruled out of action for between nine and 12 weeks.
The striker, who missed the start of the season due to a similar knee problem, suffered a reoccurrence of the injury during last weekend’s trip to Burton Albion.
Wyke worked tirelessly to return to fitness before scoring on his Sunderland debut in a 1-1 draw with Oxford United, but he now faces another frustrating spell on the sidelines.
Speaking to safc.com, Jack Ross provided an update on the striker's injury.“Unfortunately, he’s had a recurrence of the injury he had in pre-season,” explained Ross.
“If anything, its slightly worse, so we’re now looking at probably between nine and 12 weeks.”
He continued: “There’s some ligament damage, and although it doesn’t require surgery, he will be in a knee brace for a few weeks.
“We feel for him because his record over his senior playing career is actually very good in terms of his fitness, but it’s worth pointing out that the second injury is no relation to the first one.
“It’s completely separate and it’s just a bad coincidence that it’s on the same knee and it’s a similar kind of injury, so we’re disappointed because he wants to make a big contribution and he hasn’t had the chance to do that yet.
“It will probably around Christmas time or New Year before we have him available.”