Take away his mistakes and there are probably only a handful of centre halves better than him in Europe. That’s how good I think he is/can be on his day.
He gives you pretty much everything you want in a centre half - pace, strength, aerial ability, good reading of the game. It’s always been his mistakes that have let him down. He’d give away a goal every 5/6 games previously - not sure if he’s past that under Emery but the signs are good.
With that being said, I do wish he’d score a couple more from corners. Like Laursen used to!