It was bound to happen.
Guardiola having win it all in his second year, it couldn't stay the same so he had to evolve to bring some freshness to the team. If Bayern win it all this year or the next, Pep may evolve his 4/1/4/1 into a 2/3/5. Watch it
Well yeah it's obvious that formations don't explain it all but it contributes greatly.
Football is about movement but movements need a starting point which is the position in the formation.
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Myself, I've been intrigued by formations since Guardiola. Never been a football aficionado like that but '11 Barça put me into football tactics and now I like watching a match simply to understand how teams play. And it's more fascinating that now I'm part of a footy team (7 or 11 depending) and that's talks that we have before starting a match.
A few weeks ago, we played a good team (we are rookies basically) and we were playing a 3/5/2 with two holding midfielders because
we were scared to lose too much possession (they were playing a 4/1/4/1 on defense switching to a 4/3/3 on attacks) :
Problem is that our wing backs were too high and we were constantly exposed on counters. And as one of the center-backs I was always facing 2 players resulting in me being completely shyt. We were better in the second half because our defense line was higher and our wing backs lower then our shape was solider ("more solid" ?) and our build-up fluider.
We still lost 1-7.
People saying that formations and tactics are useless are wrong because it plays a key part in explaining how things happen in a match. Changing a few things can really change the outcome of the match.