That's not what he denied - he denied that there was "a deal" with United, and that therefore United would have to pay the full release clause. When asked about the idea of "signing on Monday" he said they've not heard anything official - not from United, not from the player - "it's Wednesday now and De Gea's still here, he'd have to do a medical."
So a bit of an embarrassingly premature release from SAF but nothing to suggest it's all about to go belly up.