Every defender yesterday did a great job including Rojo (minus the mistake that lead to the goal). That's also because the entire team played with more confidence and purpose.
But one performance is not an indication of anything. Even though Bailly was a beast in the last game, he can just as easily slide in and give a penalty away against Fulham in the next game.
I dislike Mourinho's methods, but he's completely right - this squad lacks maturity and that extra bit of quality (which is also a product of maturity).
Players like Bailly, Martial, Rashford emptomize the Man Utd of today - talented but immature and lacking that last final bit of quality that separate the decent players from the consistently great footballers that perform week in week out.
I don't agree with those who say that he doesn't read the game well or is saved by his pace .that's not true at all in my opinion. I think he has all the tools van djik has. iMO focus and maturity is what's lacking.