Schalke are a very poor team with high expectations. When Robbie took over they were in a huge mess, still remember one of his first games was against us and those players were atrocious, they weren't even physically good enough for the Champions League, let alone tactics. Probably the easiest win we've had in the whole season. No manager in the world could have done much better with that squad. And I'm not even mentioning all the injuries to key players during the campaign.. Resignation is a smart move, they probably have those unrealistic expectations and he can't get the freedom to rebuild the squad.