He’s not the fastest player, to be sure, but he usually makes up for it with good positioning, anticipation, vision, strength, and an engine to power through matches.
The fact that he has fallen out with Simeone is interesting, though. Saul has the reputation of being very strong minded, which has caused clashes with coaches at every level as he has progressed. I think there is an argument that only players with these sorts of strong wills (bordering on arrogance) make it to the top, but it still might not be something that Pep is looking for, as he does tend toward the extremely competitive but relatively humble demeanour.
I suppose we’ll see soon enough.