He couldn't get close, because he was covering a much larger amount of ground this season, he hasn't had the legs to play like that for about 4 years - ask Portsmouth fans. Last season, tactically, we were very compact, and Doyle was able to be use his positioning, closing down and leadership skills to influence the game. This season, we are more expansive, and without Kelly next to him, Doyle hasn't got the legs to play in this system. And he wouldn't have last season either.
Last season he was a success, this year he is 'past it' or 'it's too much of a step up', but he still has the same attributes this season, we are just not playing to his strengths, and have exposed him in the middle.