DUNEDIN, Fla. – Aaron Sanchez is showing me photos on his cell phone. They represent a roadmap of detours in a turbulent season: snapshots of the nail on his right middle finger in various states of distress.



As he taps the images, they form a chronicle. A surgeon’s handiwork, which sliced out a sliver of the nail. Red skin and dead skin. A partially split nail. Dried blood and a blood blister.



Sanchez pauses at a particularly gory shot.



“This was after the Baltimore game,” he says. “Look how ugly that looks. Look how deep that is. And I’m out there trying to pitch with my nail looking like that for seven innings, for 100 pitches, just trying to grind through it.”



We are sitting atop a picnic table in the shade of a small pavilion outside the clubhouse at the Blue Jays’ minor-league complex in Florida. Sanchez is rehabbing for the third time this season. In 34-degree heat, he has just finished throwing...