He reported the problem during the training session on Christmas day at the Aon Training Complex and Mourinho opted not to risk the club captain against the Black Cats.
Having been sacked by United in 2014, David Moyes will return to Old Trafford with relegation contenders Sunderland and will go up against Mourinho, who will want to guide his team to four-straight league wins.
Rooney has been managed twice by Moyes, but he won’t be in action due to his latest injury.
— Manchester United (@ManUtd) December 26, 2016
Henrikh Mkhitaryan was fit enough to be named on the substitutes bench, and come on in the second-half, after Mourinho confirmed he’d be back for Boxing day and hopes are he can keep himself fit.
It’s a shame that we haven’t seen Eric Bailly back in action, especially as we’ll lose him for almost four weeks in January in the Africa Cup of Nations with Ivory Coast, but it’s better to be safe than sorry, especially after the impact he’s had this season.