the guy is 26 and has played only 84 first class games, either he was always third or fourth choice, or has had alot of injuries.
Bit of both but primarily the latter, I believe he's broken his shinbone twice and done his knee in a couple of times too. Like I said, he has shown that he has all the tools but needs to stay healthy to make any real progress, and now you've got to add adapting to the PL to the obstacles in his way. Bit of a risk/reward signing, but since it's on a free not a great deal of risk for Sunderland providing they bring in other options too.