The thing is he actually played this position loads before. Reads the game very well, gets stuck in as well.
He hasn't played this position loads. He has played in a double pivot with a proper defensive midfield player alongside him.
Watching Trent and Mac playing as a double pivot in possession was like watching Gerrard and Alonso. Two exceptional deep-lying playmakers just absolutely bossing possession. The problem though is that neither of them had defensive instincts.
Mac is great on the ball and presses really well. The issue is that as soon as we lose the ball his instinct as an 8 is to press. That isn't what you require of a 6. The role of the 6 on a defensive transition is to instinctively know whether to back up the 8's on the press or to protect the centre backs.