But it obviously is... I don't know why you can't see it, but when you have a team cruising with 10 men at 2-0 up until that sub, then the manager makes a chance which opens up both wings to constant attacks and crosses, then that's quite clearly a bad mistake from the manager.
Yes, Mirallas put us in the position for that mistake by Martinez to be costly, and the rat should be relegated to the youth team until he's booted out in the summer in my opinion. And yes, if Lukaku scores both of those we win the game, but every striker will miss chances, and in the same game he put us in the position to win it.
But ultimately, if Martinez doesn't make that colossal error at 2-0 with 70 odd minutes gone, then we see out the game. It was simply awful game management yet again, and if it was the first time you'd just say "oh well, I hope he learns from it" - but the same barmy decisions have cost us over and over again now and he's bordering on suicidal in his decision making.