^ Because Suarez is one of the best players in the world.
Opponents won't have a hard time to mark (the current) Pedro. He is not dangerous in front of the goal at all. Suarez however is the most hard-working striker in the world besides Cavani and maybe Mandzukic IMO + he is the most dangerous striker out there. The opponent HAS TO try to mark him but at the same time take care of Messi and Neymar. Suarez will be a massive weapon to break down parked buses. If Lucho and the team improve their movement it'll be nearly impossible to take everyone of them out of the game.
If we assume bolded part gets implemented successfully, then we would trash opponents even without Suarez. If not, then Suarez will be not much of a factor anyway, so it basically breaks down to overall creativity and movement, which is mostly the task of middlefielders. As of now, in a lot of matches Barca looks like handball team sieging the opponents half with numbers, but not doing any penetration what so ever. The results of lack of movement and risky, but potentially creative passing. Suarez will not help, if he would roam around the box like all the others and only receive passes while being with the back to the goal and defenders.