I think the most important thing we need to do, be it with players bought (we need a hand) or tactically, is not have a game plan that relies on our wingers and second striker playing sacrificing themselves all game with defensive duties. Pressing is important but we cant rely on attackers to compensate our weak midfield, this isnt to say the players we have are shit but rather that we need more balance. Sure the way we played against Barca was great because everyone fought but also everyone was at 100 percent, we cant rely on this. Dybala needs to focus on doing what he does best creating and scoring, he needs freedom. Higuain needs to stay up forward and not need to chase down their defenders and mids. Mandzukic will do it anyway but that needs to be a bonus, not something that our game plan relies on.
We need to find balance in the midfield once again, this is why im not a huge fan of the current formation as is and I dont see how we can rectify it without changing back to 3 in the midfield.
Also quality wingers are expensive as fuck and really there arent that many attainable targets that would make much of a difference.
Dybala drifts to the right all the time and he often does well out there, he needs that freedom, he cant chase down all game.
a 4-3-2-1 is what id go for