Danilo Valiente grabs two baseballs at a time from the cart next to him behind the protective netting of the L-screen. He keeps one ball in each hand, raises them together, then makes a two-step motion from the back of the wooden ramp—a slight shuffle forward with his right followed by a longer stride with his left—before delivering what may be the best batting practice pitch in baseball.

Those buckets hold about 200 balls, and Valiente, a batting practice pitcher for the New York Yankees, exhausts that supply at least once, sometimes twice, per 15-minute on-field session before games. The on-field warm-ups, however, are only a small portion of each day's B.P. preparations. He'll throw just as many in the underground cage, too, for a daily pitch count of 400 to 500.

"Thank God that he gave me the ability to recuperate quickly, so I don't need ice or any of that stuff," he said through Yankees' Spanish-language interpreter Marlon Abreu.

Valiente's mandate for a particular session varies depending on the hitter and that night's opposing pitcher, but he's very good at what he does. It's why he was promoted to the major leagues before the 2014 season, and why Yankees teammates Aaron Judge and Gary Sanchez both have asked him to pitch in tonight's Home Run Derby.

"He doesn't miss my barrel," Judge said, while Sanchez praised Valiente for being "very consistent" in hitting a certain location. Teammate Clint Frazier, who recently joined those two in Valiente's hitting group, said the throwing is "as good as you can get."

Practice in session. Photo by Brad Penner-USA TODAY Sports

Given how many B.P. swings MLB hitters take on a daily basis, both on the field and in the cage, batting practice is a huge portion of their work, yet it's a relatively overlooked aspect of the game.

Feeding those hitters the ball may seem like a simple job, but there's an artistry and science behind good B.P. pitching. It requires a metronomic pace so the hitter can get his timing, a consistency of velocity, and a precision with command. Most big league hitters don't want down-the-middle meatballs in practice; they'd rather use those swings to work on hitting the other way or compensating for a hole in their coverage of the strike zone.

Of the roughly dozen big league hitters surveyed for this story, most said the quality of B.P. pitching was widely excellent, although longtime veteran Jonny Gomes took the contrarian view and said that, generally, big league B.P. is "not as good as you would expect."

"I think the older you get and the longer you play, probably the less you care about who you're hitting off," said Rangers third-base coach Steve Buechele, who played 11 big league seasons and now pitches B.P., but many hitters over the years have quickly named a favorite pitcher when asked.

Outfielder Jay Bruce, formerly of the Reds, said the bullpen coach from his old team, Juan "Porky" Lopez, was the best, although current Mets third-base coach Glenn Sherlock "is making his way to the top of the list very quickly." Two years ago, Ichiro Suzuki rattled off four names, and then added two more before answering the next question.

Sitting in the locker room in 2015, then Mets outfielder Kirk Nieuwenhuis offered the name of Lillian Castro as his favorite BP pitcher, and two teammates sitting at neighboring lockers immediately chimed in their affirmation of that choice. "We call it room service because it's just right there for you every time," Nieuwenhuis said. "He could knock a ball off a tee, for sure."

Nieuwenhuis then proceeded to analyze the entire cadre of Mets BP pitchers, which at the time included bench coach Bob Geren, third-base coach Tim Teufel and bullpen catcher Eric Langill and Dave Racaniello.

"You hit off them so many times that you get to know their little quirks," Nieuwenhuis said. "When Bob Geren gets tired, it turns into a little cutter. When Teuf gets tired, it turns into a two-seam [fastball]. Langy gets a little downhill action, and Rac has a little hitch but it helps you get on time."

Curtis Granderson added that pitching coach Dan Warthen "has movement like he could still pitch today" and that bullpen coach Ricky Bones, with 11 big league seasons and an All-Star appearance on the back of his baseball card, throws harder than the others.

Radar guns are a universal sight at ballparks these days, and every so often—probably by accident—someone flips the switch to make them operational hours before the game's first pitch.

Before a game at Turner Field in 2014, then-Braves manager Fredi Gonzalez delivered nearly every B.P. pitch at either 54 or 55 mph. Eddie Perez, now the club's first-base coach, was a couple ticks slower, sitting around 53 mph with his offerings. At Mets spring training a year later, bullpen catcher Dave Racaniello consistently threw in the same range, with every single pitch clocked between 52 and 55 mph.

Valiente said he almost always reaches for a four-seam fastball grip and throws a firm, but fast, pitch to the plate, at an estimated 55, maybe 60, miles per hour.

The B.P. ramp is about 45 feet from the plate, so a 55 mph pitch, when the release point is extrapolated to the normal 60-foot six-inch rubber, has an effective speed of about 74 mph.

"I haven't made it a science, it's more of a feel thing," Yankees bullpen catcher Jason Brown said. "Most of the time, I'm aiming for the middle and hoping for the best."

Yankees take B.P. during Spring Training. Photo by Reinhold Matay-USA TODAY Sports

The vast majority of major league BP pitchers are coaches, though few hitting coaches throw on-field because they are typically perched behind the cage to evaluate their players and offer feedback without the distraction of repeatedly pitching a baseball. A few managers partake, among them the Dodgers' Dave Roberts, the Red Sox' John Farrell, the Cardinals' Mike Matheny and Gonzalez when he was the Braves' skipper ("Because I can," he said at the time).

There are exceptions: clubs sometimes hire local lefties, whether an amateur or recent retiree, before facing a southpaw if every coach on staff is a righty. Hall of Fame southpaw Sandy Koufax, who retired in 1966, pitched B.P. to the Dodgers before his old club faced four lefty Yankees starters in the 1981 World Series.

By and large, however, B.P. pitchers are middle-aged coaches who used to play pro ball at some level. Valiente, 51, grew up in Rincón, part of the Boyeros borough of Havana, about a 90-minute drive from the capital city's downtown. He played in Cuba's top minor leagues, self-deprecatingly shaking his outstretched hand in the universal sign for "so-so" when asked to evaluate his ability, though he admitted he once won a batting title in that division. Those teams didn't have many coaches, so the players alternated throwing B.P. to each other. That's when he learned he had a knack for the task.

After marrying an American woman, Valiente moved to the U.S. in 2006, settling in Tampa. There, he approached Yankees executive Mark Newman to ask for a job; Valiente began helping informally and, by 2007, he was an official member of the organization. He coached at three different minor league levels, as well as at spring training where he gained renown for his superlative skill.

"Little by little, I started pitching B.P.," he said, "and eventually they kept calling me back to do that."

Any particular round of BP is just one throwing session in a series of nearly 200 consecutive spring training and regular season days. Some days a coach may be more caffeinated or better rested than others.

"You can tell, you can tell," Romine said. "Maybe they slept good, maybe their arm feels good, but you can also tell the other way around. These guys throw every freaking day. I mean, a lot of pitches, and they take it really seriously. If they throw a ball, they get mad."

B.P. can be just one component of a coach's throwing obligations for the day. The Yankees' Brown, for instance, plays long toss with the catchers and warms up the pitchers, too. "My day's just getting started," Brown said of B.P.

All of the BP pitchers polled for this story gave similar advice about finding repeatable mechanics and throwing free and easy.

"To me, that's what it's all about: getting in a rhythm and just letting it go, being natural," Buechele said.

Photo by Aaron Doster-USA TODAY Sports

Whether the hours of daily B.P. are actually worthwhile is up for debate. Some hitters swear by it, others avoid and most register an opinion in between. It's a way to get loose, hone one's timing, experiment with something new and get the hands working so the muscle memory is sharp for the swings that matter.

"I think batting practice is pretty instrumental in preparing for a game," Yankees catcher Austin Romine said, noting that, as a backup, he takes hundreds of cuts before and during play so that he's ready for pinch-hitting opportunities.

"I think it definitely maps the path and the direction that you want to go," Frazier said.

Ichiro warned against a good BP round producing overconfidence in the game, then added, "At the same time, maybe you don't feel as good during batting practice, so you become a little bit more focused or more selective trying not go all out—maybe you're a little more humble—so you're up there not going at it and you might have a better at bat."

One National League scout said he likes to watch other clubs' taking batting practice, hoping to glean insight into hitters' mechanics and into their points of emphasis, which often signal a recent weakness.

John Olshan, the general manager of TrackMan Baseball (whose radars power Statcast), said B.P. and the Home Run Derby are proof that power is "a competition-independent hitting statistic," with the speed of the pitch having a negligible impact on distance traveled once it's hit. (The old mantra of "the harder it goes in, the harder it goes out" is vastly overstated.) Olshan said only 35 B.P. swings with exit-velocity and launch-angle data points are needed to accurately project a player's isolated power—his rate of slugging extra-base hits. He added that some big league clubs turn on Statcast during B.P. to scout opposing hitters.

Those sources are saying there's both objective and subjective merit in scouting B.P. Really.