When a good or promising player transforms into a crap player due to lack of confidence, usually there are still signs that the quality is in there somewhere waiting to be reawoken (I got that sense from Ireland, for example). You'll see a good touch here and there, fleeting glimpses of talent which are then cancelled out by bad decisions.
From what I saw of Delph while MON was still here, I had a lot of hope for him. He seemed to have assurance and great close control, plus a lot of determination. Since that knee injury of his, however, he's given nothing to base any more hope on. His touch is now terrible and his forward passing is shambolic. Defensively he offers little. Overall he's like a John Hogg with more dangerous, less effective tackling. In fact his tackling is worse than ever which sadly suggests he hasn't learnt anything since arriving here, and leaves a strong possibility he'll pick up another long injury.
A loan could be the best thing for him. I just don't think he has a role with us. Clark and even Herd (who I think is shaky) are better at DM, and the queue for attacking midfield positions is long enough for Delph not to deserve a look-in.