Sunderland manager David Moyes has revealed that Duncan Watmore could need a second operation on his injured knee after suffering a setback in his recovery.

The 23-year-old was ruled out for the rest of the season after damaging his anterior cruciate ligament in December of last year, but recently returned to light training.

However, Moyes confirmed that the midfielder has felt pain in his knee during running sessions and will see a specialist this week to discover whether he will require further surgery.

"Duncan Watmore might be needing a little bit of work done on his knee. Obviously, he's not back, but he might be needing a little bit more surgery on his knee," Moyes told reporters.

"He's been feeling it - he's been running a little bit - so he'll see the surgeon this week."

Watmore had made 14 Premier League appearances for the struggling Black Cats this season before his injury.