His stuff is awesome. He just can't keep it in the strike zone, yet.
There's no way you can throw Maples out there in the playoffs. You can't possibly trust him. And I would love to see him succeed, I know as of last year the Cubs internal scouting had him graded out with the best fastball and slider in the entire system, MLB included, but his control has been terrible every chance he's got at the MLB level.