Normally often does not apply in the game
I had 74% possession, played with the same tactics he had (442 classic), had superior quality team, he had more than half of his players out of place, and still only got a 1-0 win
We shouldn't take it easy just because we're playing an abandoned team. Last season i almost won the championship because the leader drew one game to an illegal formation team. Also i saw one player which was doing a good season loose a match to an illegal formation by 2-0. So Having a ton of possession doesn't guarantee you a win. You may rotate your squad, but always take your best players as subs, and prepare a counter formation in order to prevent a surprise (as stated before, i could not do this, so i struggled).