On a wet and dreary afternoon in Seattle last week, Marco Gonzales eased into his car and drove from his home on Capitol Hill to T-Mobile Park, where he was met with silence the moment he pushed open the clubhouse doors.



Without fanfare, Gonzales put into motion another day of a comprehensive workout program designed to help him replicate — if not eclipse — his breakout season of 2018.



Because it was a Wednesday, Gonzales had already taken a morning yoga class with his wife, Monica. At the ballpark, he would do arm-care exercises followed by some running. It was technically an off day, though with Gonzales it’s never really an off day.



“Every single day, when I walk through the doors, I know what my day is going to look like down to the minute,” Gonzales said. “I’ve seen how fragile I’ve been. I never want to go back to that.



“I know how my body needs to feel. I know how I want my body to feel. If...