Not sure about natural abilities as a footballer but he certainly is an athlete. There is going to be an expectation to perform following his previous seasons, perhaps everything has moved too fast? He was very good at Villa, which saw him dislodge Corluka and then become an England international - oh and the young player of the year award. A lot in a short go.
Like Friedel (I use him as an example since it's topical) - Walker needs to understand his current limitations and play to them (sure the manager might want more than he can offer) and he also must keep fully focused as I think he can lapse, maybe like Friedel this comes with experience?
He actually started off as a striker and good shot he has (so it seems), perhaps his athletisism saw he capable enough to be a full-back?
Perhaps just like Glen Johnson, he cannot play to his strengths with a player like Lennon in front of him (should he have an inverted winger in front?)
The kid is young and I know you can argue so was Bale, etc but I'm sure he'll come good and be here for the long stay.