Not sure he will start the big games in CL. Team seems to have settled well with the current formation and I can't see Valverde changing that for big games
If Valverde does that, he makes a big mistake...
The current formation is based on a semi-defending football, and the attack formation is Messi - alone (usually coming from deep). Suarez can't do anything alone or without Messi, so either Alba or Roberto has to do long runs, and do their usual things to support the attach. Paulinho is very instinctively dangerous in front of the goal, but before he arrives on the right second, the ball needs to get there somehow.
So far this defensive formation has been successful, but it is definitely not the real Barca style. It is a compromise, that Valverde came out with, when Dembele got injured and it became obvious that neither Delouf nor Dennis can really play successfully up there.
But when Dembele is available and is in form again (didn't he deserve a place on the bench at least to mentally support him???), then playing the same defensive game and leaving the rest on Messi's creative genius, would be a great mistake.
Just as it's been a mistake not playing Semedo and Roberto as a midfielder rather.
A 100+ M new signing needs to play, otherwise sooner or later he'll get close to a crisis situation, that nobody wants.
Valverde is a typical "play it safe" type of coach, a very good coach and very successful so far, but some of the CL games clearly showed that on the international ground, it is often not enough in itself.