Paddy McNair was the one to fill the void in Manchester United's frail defence in recent victories over West Ham and Everton, after Louis van Gaal was hit with a back-line injury crisis.
The 19-year-old performed exceptionally well in both matches, especially for a youngster evidently targeted to get the better of by two pacey and corporeal strikers in Romelu Lukaku and Enner Valencia, alongside new signing Marcos Rojo.
McNair was expected to be handed a Nothern Ireland call-up ahead of the Euro 2016 qualifiers against Faroe Islands and Greece.
The setback leaves the United boss in a real quandary after Luke Shaw also picked up a knee injury on Sunday and was forced off, although he is expected to have at least one of Chris Smalling, Phil Jones and Jonny Evans back for the trip to West Brom after the international break.
Tyler Blackett, the only recurring United defender this season before his suspension, returned as a late substitute against Everton.
