I think Rafa will pick apart Del Potro like a vulture with a coyote carcass.
Toying with Juan Martin's relative immobility, Rafa finds creative ways to escape from love-30, love-40 and love-30 starts to his first three service games, 3-2....Living dangerously, Rafa saves three break points at 4 all, missed opportunities that may not come again, 5-4....Rafa turns it up a notch, and there's the break, 6-4. The set's result seemed preordained.
2nd set: A very sharp Rafa cruises 6-1.
3rd set: Pickin' dead flesh from his teeth with a gold toothpick, Nadal breaks immediately, 1-love....a second break follows for 4-1....looking invincible Rafa takes the match 6-2.
Thiem is going to have a long day on Sunday by the looks of it.