Obviously Nadal is the favorite, but if one has seen their past matches, one interesting aspect is that Schwartzman small size gives him kind of an advantage: probably because of this, he loves to get the ball on the rise, which is a very good (even if obviously risky) strategy against Nadal. Surely better than to lay back and be killed by the top spin. That's why most of their past matches had stretches of very competitive play, and why a "peak Schwartzman" is a good candidate for an upset against a so-so Nadal. Unfortunately, it is the other way around and we have a so-so Schwartzman against at least a pretty good version of Nadal.
Even so I will go with a twist in the plot: Schwartzman gets the first set and will lead by a break in the second. Then...