Might not take as long as we think. Frenkie has always been in decent physical conditioning. Coutinho spent the year at Bayern, Pjanic -Juventus, Trincao - Benfica, Fati might have a way to go yet but that's the case anyway because he's young. So long as dembele is fit that will be the best physical health he's been in, in 3 years lol. Roberto has always been one of the more physically fit players in the squad. For all of alba's faults he's capable of running up and down the wing.
Messi, Griezmann, Pique and Busquets are probably the players you'd target to get better physical conditioning out of. Pique tbf to him is usually fit so I'm not sure he even belongs in that list. Busquets shouldn't even be starting tbh.
Pique was never the biggest problem of not able to run anymore. The guy is no Varane, but never seen him being outpaced continuesly like Bartra-Bale duel was. Pique's problem is always to get his head and concentration into the game.
Griezmann works his butt off, but lacks on the ball technique. His off the ball movement and defensive work is good.
Left us only with Busquets & Messi, who don't have the legs anymore for this game. Way better than last year with Busquets, Vidal, Rakitic, Suarez & Messi in the squad, without legs.
We have 2 major overhauls to overcome;
The mental aspect in our defense (Alba, Lenglet, Pique & MAtS), who seem to struggle when the pressure is real.
Physique from the squad, where we already made major steps by releasing 3 deadweight players.
Curious to see if Coutinho can maintain this kind of play, and Messi can maintain his role upfront and he won't be the focal point of every attack.