That's not really true, though. Bergvall was our player of the year playing almost all his minutes as a CM not a 10, and he's been pretty shocking as a 10 under Frank - that position really doesn't play to his strengths. Xavi's been a disappointment so far but he's still miles better than Bergvall as a 10 imo. If anything we've dropped Bergvall for Palhinha/Gray.
Frank clearly doesn't trust Bergvall deeper as he's a bit of a maverick and not that positionally disciplined. We need to get him games playing deeper, though, as it's his best position and he was brilliant much of last season.
Bergvall could crush it at the 6 for us so hard- he has a mean streak in him and will square up to anybody. I agree that Frank is totally blowing it playing him at the 10 though. Its weird but Bergvall is even a better LM/RM than he is a CAM.

