Mertesacker had a lot of good qualities. I'm just saying that pace and technique weren't two of them, and I don't think they're needed to pass the ball out from the back. You look at a side like Brighton where they have taught someone like Lewis Dunk to do it properly late in his career, and you think there's every chance that Holding can too. I think technical ability is a little overrated when we're talking about centrebacks. There are one or two players like Marquinhos out there who could school everyone as a midfielder too, but in general even the best defenders are going to be poorer on the ball than your average central midfielder. And top teams aren't dropping central mids into the defence just to pass the ball around better.
Either way I'm not suggesting he should start for us, I'm just saying maybe Arteta likes him. He was a bit overrated before his injury, and since he came back opinion has swung to the point where people now talk about him like he's Igors Stepanovs.