I've always been a big fan of Petch. You dont need to be a great player to be able to coach, and I knew of his work with Silvija Talaja. I thought his one drawback was he'd only coached women.
But a good coach (like a good teacher

) has to have the ability to analyse, correct, motivate and change aspects of their pupil while building up their confidence. Mark can do this as well as being young enough to understand a stroppy teenager.
MacEnroe would make a terrible coach on a weekly basis. (Not that he would do that. But there was some talk that Andy should have a few weeks with him) His temperament isn't suited to it. Petch's is.