He was great in the championship, as was Leadbitter, but neither of them were PL midfielders. We signed De Roon and we had Forshaw, they probably should have been the upgrade to Clayton and Leadbitter but losing Leadbitter was more than just his ability, it was his organisation and leadership which was more difficult to replace and everyone else suffered. We probably should have prioritised a Leadbitter upgrade to play alongside De Roon who we have seen has gone on to have a top level career. Instead we were forced into 3 CMs and even though De Roon played as the front of those 3 he would have been more suited to playing his own game and having Ramirez ahead of the 2 instead of out wide.
Clayton lacked the pace for the PL and he slowed things down too much and his weekly booking for pulling a player back was happening earlier in games meaning he had to sit extra deep to not be forced to do it again. Harsh realities of stepping up to the PL is that some of the best players that got you there will never be good enough for that step up.