Ask different people, including Hernandez, and the descriptors are different: Immature. Perfectionist. Emotional. All could be used to describe the 21-year-old outfielder, whom the Pirates acquired from the Braves in a four-player June deal that sent Nate McLouth to Atlanta. But all may also inadvertently mask some of Hernandez's greatest strengths: his drive and passion.
Hernandez's temper has come under some scrutiny already this season, with Altoona manager Matt Walbeck twice removing the outfielder from games because of immature and disrespectful reactions. But while that could be easy reason to prematurely label Hernandez as another organizational top prospect primed to underachieve, the Pirates aren't looking at these occasional episodes as a long-term issue.
In fact, as director of player development Kyle Stark asserts, the root of some of these initial issues is not the concern.
"I think what we're dealing with is a young man at Double-A who is a perfectionist," said Stark. "He has high expectations for himself and he doesn't handle it well when he lets him down. He's learning how to channel those responses and how to handle failure.
"We're not dealing with a bad kid," Stark continued. "We're dealing with a good young man who has high expectations for himself and who cares greatly about his performance. The root issue at heart here is a good thing. It's trying to channel those emotions for the better."
By all accounts, Hernandez has, in the past three months, already improved in that respect.
"He has looked better," Walbeck said. "It's been brought to his attention that we do notice it. He seems to be having more fun. He has more of an attitude that shows some professionalism. He's really making some big strides here toward jumping to the next level."
"My attitude is now good," said Hernandez, a bubbling Venezuelan native, who exudes self-confidence with every question he answers. "I'm working hard on that. Things are much better now. When I go to the field, I want to help the team. If there's a runner on second base, I want to move him over. If he's at third base, I want the RBI. I want to help the team. Sometimes when I don't do that, I get mad at myself. But now, it's much better."
The byproduct of Hernandez learning how to keep his emotions in check is the ability to better let his skills play out. And there is little debate that he has intriguing raw talent.
Hernandez's defense -- highlighted by his above-average arm and speed -- is certainly the most polished at this point. His speed is a natural gift, though one he's still learning to better utilize. In 80 games with Altoona, Hernandez has swiped just nine bases and made only 14 attempts in all, surprisingly low numbers for a player whom scouts have said has the potential to steal 40 bases a season in the Majors.
"Everybody says I have this awesome speed," said Hernandez, who was ranked by Baseball America as the 62nd-best prospect entering the season. "I don't have a lot of stolen bases. I don't know why. I think maybe next year, I'll be more comfortable to steal a base. Maybe next year, I try 40 or 50."
That lower-than-expected number is partially the result of Hernandez being a bit hesitant to run when on base. The larger underlying problem -- and one area that has been targeted in his development -- is that Hernandez hasn't been getting on base enough to maximize his speed.
Hernandez's .258 batting average isn't the issue. It's the .306 on-base percentage that Hernandez has posted with Altoona that is more the concern. It's a figure that is way too low for a player projected to be a leadoff hitter and lineup catalyst. And it's the result of Hernandez drawing just 21 walks in 345 plate appearances, an average of one walk per 16 at-bats.
Conversely, Hernandez has struck out 72 times.
"He needs to -- or will, probably, the more he plays -- become more selective at the plate and swing at pitches he has more of a solid chance at making contact," Walbeck said. "I think he's been trying to do too much at times and reaching and swinging out of the zone instead of taking the walks."
Part of that, too, stems from those already-identified issues of attempted perfectionism. With a runner on base, Hernandez has been more inclined to go for the RBI hit than take the walk. His desire to be a catalyst has, in the past, trumped his patience.
"We talked a little bit about the maturity issues and the discipline of doing the right thing even if it's not the outcome that he might want," Stark said. "I think it's something we should see improvement in."
With the focused guidance Hernandez is getting from the Pirates' development team, there is still a widespread belief that Hernandez can become a dynamic Major League leadoff hitter and center fielder in the not too distant future. He was a main piece in the McLouth deal, making his progression through the Minors more publicly scrutinized than most prospects in the system.
Hernandez's answer to all this? He points to his passion and intensity, and where it will guide him now that he is channeling it correctly.
"I've worked hard and I'm playing hard so that when I get called up to the Pirates, people watch and say I'm ready," Hernandez said. "I have to work every day. I try to work very hard so that when I get the call to the big leagues, I'm ready."
And then that confidence peeks out again, as he smiles and adds: "And I think there will be a competition in center field next year."
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.