We obviously need to upgrade him, but I'd rather upgrade DM before him (if we have funds to buy just 1 player from these two positions).
He obviously isnt some elite defender, but he's a decent reader of the game, passes well (which is necessary to play the style Ole wants), and he is good at guiding opposition players away from goal to less dangerous areas. He wont be the one making the tackle but one of the things I've notices is that he just closes down the path in which the opposition is expected to run forcing them to go wider - obviously doesn't always work out but that's not the worst strategy when you have AWB on the flank.
Having said that, we quite clearly need a better CB - someone better in the air from dead balls and someone who can impose himself against opposition strikers. One of the things working for him is that the 2 DMs are not really DMs, his competition is with Bailly and Tuanzebe and the fact that on his worse days he still produces a 4/10 performance unlike Bailly who is as capable of putting in a 2/10 performance as an 8/10 performance