Assuming you're referring to whether he can get us promoted MB, His first 4 seasons were awesome for us. After that, it was as much to do with not being able to compete once teams sussed us out and we lost O'Connell.
He always said we had to be at our 100% best to get anything in the Prem. He did that for a while, but eventually, the quality of the squad let him down. I believe he is a good man manager, particularly with his own club which I think gets that extra 10% out of him, and in turn gets it out of his players.
Now, a lot will depend on who he can keep, and who he can bring in, but Wes will do fine in the Champ, and with Trusty, McAtee for another season, and Archer up top, we've got one heck of a spine to the team. A couple of additions would maybe make a difference, but even with the current squad, I think we'd have enough at that level.
If we did go up however, then yes, he'd struggle again without some serious investment.