I'd say there were a few mitigating circumstances.
He injured himself prior to coming here then had niggly injuries the entire time.
He also didn't have a proper pre-season with the club.
On top of that he just generally didn't seem happy here nor did he seem to settle.
Not totally indicative of lack of skill or effort; it can happen to the best of players. I hate to compare the EPL to the A-League, but look at Di Maria at Man Utd; good player, but just didn't fit there.
p.s. I noticed he banned me on twitter. It might be because I linked to the video of 'Wake Up Jeff'.