This was really unexpected. Sepp Blatter has ridden out many storms before - he's faced persistent criticism for the way he runs world football, particularly from Europe.
I was at his press conference on Friday - three days ago - and he was really combative, and he answered question after question after question for him justifying his suitability to run world football.
All he said, every single time, was: "Well, look what happened yesterday, look at congress, everyone in the world voted and they voted for me, and I believe I'm the man to turn this round."
What has changed since then, we don't know - clearly we hope we will at some stage, but maybe he's just realised that the pressure's got too much for him.
Maybe he's realised that the support he's been trumpeting on Friday wasn't as good as he thought.
But all bets are off from here on in, as far as world football is concerned. We could be looking at anything from this corruption, into what happens again - more scrutiny on the 2018 and 2022 World Cups.