McTominay was replaced by Paul Pogba after 45 minutes of the 4-1 win at Newcastle
Manchester United midfielder Scott McTominay could be out for up to a month with a knee injury.
The 23-year-old was hurt in the 4-1 win against Newcastle and left the Boxing Day game at Old Trafford on crutches.
McTominay did not play in the 2-0 victory at Burnley on Saturday.
"I don't know if it's three or four weeks. It might be something like this. We've just got to find a way through it," said United boss Ole Gunnar Solskjaer.
Midfielder Paul Pogba was also absent from the Manchester United squad for the trip to Turf Moor.
The France international recently returned from an ankle injury that had sidelined him since September and played 45 minutes against Newcastle.
"He's been out for a long while and he didn't feel right, he reacted to that one," added Solskjaer.
"We'll just have to take our time and get him ready for next time."
Source: bbc.com