He pretty much exclusively has used 4-3-3 and 4-3-1-2 in his career.
I agree with the width comment but the overriding tactic/philosophy he uses is the same in both (i.e. high line, hundreds short passes, rarely go direct, if plan A isn't working stick with it, play through central regista etc).
We've seen deviation from Plan A which was basically to just put all the attackers on the pitch at once. Which is pretty standard for most coaches. It's clear that Plan B is Dybala at CAM and we've seen it. I think a better current Plan B would be wingers/crosses and we haven't seen that but we haven't had wingers either.
I can't accept that he doesn't want to go direct. Napoli was absolutely lethal going direct. Mertens was behind the line every match that we saw. Have we seen it that much at Juve? Not so far. Ronaldo goes in behind and screams at the air when he doesn't get the ball. Dybala goes in behind. Higuain doesn't because he's slow. Most of the time the opposition is really deep though so it's hard.
I think he will never change the regista between 2 CBs. That one I really have to agree.
The high line so far is concrete as well although there really hasn't been a reason to sit deep. I think we'll have to see how the UCL unfolds for the answer to that question.
But lots of successful coaches have some central tenants that are sometimes worth being consistent with. It's still hard to evaluate him at Juve because we haven't had a knockout UCL tie yet. And we breezed the group so there weren't a ton of adjustments he had to make.
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But that was a necessity when the squad has 1.5 wingers. Maybe a formation with 3 man backline but Sarri refuses to change to a 3 man backline
There are times I want to see something like a 3-4-1-2 but I understand when Sarri says that a 3 man backline always turns into a 5 man backline and we've seen evidence of that when Conte was here and I can't really disagree with that thought.
I think it's better long-term to work out a formation that plays with 4 at the back and if you can work in 3 at the back to win a couple league matches here and there, fine. I would prefer that actually but I don't think it will stop us from winning the UCL. We would have to do that on the back of a consistent play style, I think.