Newcastle manager Eddie Howe revealed on Tuesday that England defender Dan Byrne will be out for the next four to six weeks.
The Weir-Tyne derby defeat on Sunday was made worse for Howe when Byrne was taken to hospital after a serious collision with Sunderland defender Nordi Mukiele.
Byrne received medical treatment on the pitch before attempting to continue playing but was eventually taken off in the 42nd minute to be replaced by Fabian Scher.
Newcastle's attention now turns to Wednesday's League Cup quarter-final clash with Fulham and, speaking ahead of that match, Howe admitted that Byrne's injury was a “big blow” for the club.
“It was kind of under the radar in terms of the review of the game, the importance of Dan and losing him and just because of everything he brings to the team. It was a big blow for us. I think he has been excellent in recent weeks.
It's a problem with the ribs as well as some lung problems. We wish him well, it will probably take him about four to six weeks”, Howe told a news conference.
Byrne's injury further compounds Howe's defensive concerns, with Kieran Trippier and Emil Kraft still out and the Newcastle manager admitting their defence looks “vulnerable”.