The Argentine, who had spent seven months on the sidelines with knee ligament damage, returned to the starting XI alongside Chris Smalling in Switzerland.
And he picked up virtually from where he left off, producing important interceptions and leading the line with composure. He even rattled the bar with a powerful drive in the first half.
Speaking after the game, Mourinho was quick to make note of just how important the Argentine will be to the squad for the rest of the campaign.
“I agree with you, I think he played very well,” he said.
“He could be playing a couple of weeks ago, we didn’t need to rush or push him into that situation.
“But he was training with the team for quite a long time, we had to try 45 minutes with the Under-23 team, we knew that Marcos was ready, the doubt is 90 minutes, less than 90.
“But he controlled the first-half really easy, he didn’t have to be in physical demanding and he controlled very well his game.
“So we are happy to have him and we need that.”
With Phil Jones and Eric Bailly continuing to battle with niggling injuries, Mourinho would have been desperate to welcome back a man who spearheaded his side’s defensive resolve for the majority of last season.
And he didn’t disappoint. To spend seven months away from the game and come straight back into the starting XI in the Champions League takes serious guts and self-belief, but Rojo made the whole thing look easy, providing a welcome source of assurance as United’s full-backs crumbled in miserable fashion during the latter stages.
Supporters will just pray to see the 27-year-old stay fit ahead of a busy December month.