The first bullpen session Hernandez caught at Salt River Fields was Lopez's, and the two have grown closer ever since. After a season apart -- Hernandez split time between the big leagues and rehab assignments in Triple-A Reno, while Lopez spent most of his first season stateside at Double-A Mobile -- Lopez is back throwing to Hernandez, now as teammates on the Salt River Rafters in the Arizona Fall League.
"We try to have a good relationship, pitcher and catcher," Hernandez said. "Right now, he's like my brother."
Having caught Lopez, Hernandez has a unique perspective on the young pitcher. He called Lopez's slider, which has a sharp, late break, his out-pitch, but he doesn't discount his mid-90s fastball, either. Lopez rounds out his arsenal with a curveball and a changeup.
The pitcher-catcher dynamic extends beyond the 60 feet, 6 inches on the diamond, though. As fellow Spanish speakers, Hernandez is one of a handful of players in the organization Lopez has been able to bond with.
"The language [difference] affects us a lot," Lopez said. "When you come here, you have different teammates on your new team. You have to get accustomed to it."
Recently, Lopez opened up to Hernandez about the difficulties of defecting from Cuba and leaving his home, friends and family behind at just 21.
"For him, it was really hard," Hernandez said. "But he's so happy to be here. He wants to work hard to get better and get to the big leagues one day."
Lopez's AFL assignment comes after a turbulent first season in the D-backs' organization.
When Lopez was unable to board the Mobile BayBears' team bus on July 2, according to azcentral.com, and turned up a day later on social media in Miami, it might have spoken to his maturity, or lack thereof.
Ask his AFL coach Larry Pardo, though, and he questions what 22-year-olds are fully responsible. Not all 22-year-olds, however, are awarded $8 million signing bonuses. But not all 22-year-olds are recently defected from Cuba, either, and in a country where they don't speak the language.
After being assigned to Double-A Mobile out of Spring Training, Lopez endured a year of highs and lows, both on and off the field. In nine starts and 48 innings with Mobile, the lanky right-hander posted a 4.69 ERA with 32 strikeouts and 24 walks.
Once the D-backs tracked Lopez down, he pitched only three more games outside the state of Arizona.
"It's something very personal, and it's in the past," Lopez said of the July incident. "Going through all of this, it helps you mature. It pushes you to focus more on your work so you can achieve your goals."
Lopez has made six starts in the Fall League, showing similar inconsistency to what was present in Double-A. In three starts, he's allowed two or fewer earned runs and struck out at least five. But in the other three, he's allowed 17 total hits and 11 earned runs in 10 1/3 combined innings.
Thanks to the pace-of-play rules in the Fall League, Lopez is able to get into more of a rhythm on the mound -- at least that's what Hernandez, Pardo and the D-backs are hoping happens. Hernandez believes Lopez is at his best when working at a quick pace.
"Everybody knows Lopi's got good stuff," Hernandez said. "I feel like he's got to command his pitches and be more relaxing and learn about this game, because this game takes a lot mentally, not only physically.
"But he's gonna get it. He's gonna get it."