He was great on the ball (well he IS great on the ball imo, as good as he needs to be at first team level) but I thought he had the same problem as Yaya in this system, without the ball. No lack of effort, but he struggled to close down effectively. It was easier to get away from him than it is the others.
He may find an extra yard of acceleration from somewhere when match sharp, but if he doesn't then, like Yaya v Stauer, no matter how much distance he covers, he will leave an extra half yard of spece compared to others & he would be more effective in a slightly different kind of setup, where he can spray passes around & pick up loose balls rather than always pressing. Whether Pep has in mind to vary it in that way, I have no idea, but we were linked with Kroos who does that & he had Yaya at Barca of course.