The Ivorian replaced Antonio Valencia after he sat out his suspension at Selhurst Park and put in a spectacular showing in the new role.
He gave supporters a scare after he was clutching his knee five minutes into the first-half, but he carried on until he was forced off in the second-half through injury.
Speaking after the game, he claimed Bailly had suffered a problem with his other knee.
“We don’t know (how serious it is). It is not the same knee, it is the other one, so it is not previous injury. He has a problem, we don’t know the dimension. He showed character to try and try until he reached the limit,” he said.
There were worries that he suffered an injury on the same knee that had already kept him on the sidelines, but Mourinho made it clear after the game that it wasn’t the case.
He’s been wonderful for United but should be featuring in the central role where his skill set is best utilised, there’s no doubt that once Valencia is back in the squad, Bailly will take over from Marcos Rojo.
It remains to be seen how serious his injury is but with the Africa Cup of Nations coming up in January, he could be forced to sit out.