Was he shit because he couldn't do it, or shit because he didn't want to do it? That's where being a strong manager has to come into play. Because he can't be a lone striker anymore, and it would be madness for him to displace Sigurdsson.At the time he was saying it was where he saw himself playing to continue his career at the top, so I'd guess it's safe to say that he couldn't do it to a high enough level.
If we insist on shoe-Horning him into the side with Sigurdsson, then hasn't Sigurdsson played centre mid quite successfully for Iceland?
Personally, I'd much rather have Davies in there with his movement and forward running. Even when he's not in top form he gives us something different than any other player we have.