At the time, Hernandez, who was one of the club's best relievers in 2011 and '12, had a 5.59 ERA.
"It's a challenge for us," D-backs manager Kirk Gibson said of the club's decision. "What do you do, the guy's struggling and you understand where he's at and what's going on with his performance, but what do you do? Do you stick with him? Do you try and encourage? Do you work through it? Do you put him in low-leverage situations? Do you keep putting him in high-leverage situations? Do you send him to Triple-A? ... We went through it all, and then the reality is when we finally sent him down he was relieved."
Hernandez went to Reno and worked with Aces pitching coach Mike Parrott to refine his mechanics, and he began throwing his two-seam fastball a little more often.
More than that, though, the demotion relieved some of the pressure and allowed Hernandez to find joy on the mound once again.
"It was one of the most frustrating years of my life, just in general," Hernandez said. "It was a combination of everything. There were things I was going through in my personal life."
While not getting into specifics, his off-field difficulties were weighing heavily on his mind beginning toward the end of the 2012 season. Then, when he started struggling on the field in 2013, it just added to his issues.
"Just knowing in the back of my mind that I'm way better than how I was pitching," Hernandez said of his frustration.
His teammates could tell that something was not quite right.
"I think you could see it in his performance," fellow reliever Brad Ziegler said. "He wasn't the same guy, and we all knew it. When you talked to him you wouldn't know anything was different, but you just could kind of tell something had to be different because he wasn't pitching as well as he has before. Sometimes you want to try to fix things within the realm of baseball, and sometimes the fix is outside of baseball."
In Hernandez's case, it appears the fix was a combination of both, but it began while he was in Reno.
When the team recalled him at the beginning of September, Hernandez did not allow a run in the first nine appearances, and he allowed just one earned run while holding opponents to a .130 batting average over 14 appearances for a 0.64 ERA.
The Hernandez of 2011 and '12 was back, and while his overall numbers would still not be great, the strong finish allowed him to enter the offseason with a little peace of mind.
"It made me feel like I still had it," Hernandez said.
While the late success gave him confidence for the offseason, the early struggles provided him with the fuel to put in extra effort during the offseason.
"Obviously, when you don't have the year you want to have, it forces you to change a few things, work a little harder, and that's just in general with your daily routine and workouts," Hernandez said.
Hernandez ran more during the offseason while also changing his diet, and the result was that he lost around 20 pounds and reported to camp weighing 238.
"Every morning I step on the scale and I say I need to stay right here," Hernandez said. "It fluctuates, but it's probably the lightest I've been in the big leagues. I feel more in shape, and it can give you a better edge when you go out there. For me, it just feels better."
The mechanical change from last year remains. He raised his arm angle a bit so that he can stay on top of the ball better and get more of a downhill plane with his four-seam fastball, and he will continue to mix in a two-seamer to keep hitters honest.
The personal issues from a year ago have also been dealt with.
"Going into this Spring Training, I just feel like I'm in a clear state of mind," Hernandez said. "I just want to continue to put one foot in front of the other."
Even though it's early in camp, the difference is noticeable to everyone in the clubhouse.
"If you just look at his body, he's in better shape this year," Gibson said. "He's a lot leaner. His mind is right. He's just in a better spot mentally and physically."