The 20-year-old defender suffered the injury whilst on Northern Ireland duty. He was injured in the 13th minute during Northern Ireland’s 1-1 draw against Finland on Sunday, but continued till the 51st minute before being replaced.
According to reports from The Mirror, the young defender spent the Sunday night in hospital and will remain in the Finnish capital for another night as a precautionary measure.
McNair could likely to miss Saturday’s trip to Goodison Park, but his absence will hardly make any difference to United’s preparation ahead of the match. He has made only one substitute appearance for United this season, and wouldn’t have featured in the starting XI against Everton.