Two outs, bottom of the ninth, Yankees leading, 2-1. Any protestations about baseball's pace get thrown out the window in these moments; what's unfolding is pure cuticle-destroying drama. The Angels have a man on first, and one of the best hitters in the game is on deck. This is it.
Albertin Chapman, the Yankees' closer, offers a look toward Chris Young leading off first, then sets and delivers an 84 mph backdoor slider to Ian Kinsler. The pitch is a bit off the plate, but Chapman gets a generous strike call. Then he brings the heat. After a relatively pedestrian 99 mph fastball that gets fouled off, he fires four straight 101 mph missiles. Chapman, sweating but fully composed, throws each like it's nothing, and although the Yankees are in their road grays at Angel Stadium, there are plenty of pinstripe-clad fans on their feet cheering each delivery. Speed thrills.
But we'll get back to that at-bat in a bit. Back home at Yankee Stadium -- like in every ballpark -- some of the grandest fireworks explode hundreds of feet from the field, in the top-right corner of the center-field video board. It's a simple piece of electrical engineering -- a third digit on the radar gun. These days, that 100 mph heat has grown more common than ever, but it's no less exciting.

"Perhaps the most fascinating element in sports is speed," Dave Anderson wrote in The New York Times 40 years ago this month. And the players today are still amazed by the power arms. "You see that third digit," Christopher Austin says, "it's a whole different level there. It's pretty intimidating." But the first baseman stops himself. Is he willing to let pitchers know that their best fastball can get inside his head? "Oh, heck no! You just go up there and try to hit it. Go up there and compete."
Austin doesn't have to worry about facing baseball's most fearsome fire-breather. Across the clubhouse, hidden behind a large pillar, sits the hardest thrower in MLB history. For several years now, MLB.com's list of the fastest pitches of the season, as measured by Statcast™, has featured a Chapman Filter, which removes the southpaw's entries; without it, the chart had proven redundant and useless. This season, the Cardinals' Jordan Hicks has been throwing most of the fastest pitches, but Chapman still has history on his side.
He is the Cuban Missile, the Sultan of Swift, the Viceroy of Velocity, but Chapman's left arm is merely one divine instrument in a sport obsessed with speed. And it's not just fastball readings. So much of what happens during the course of a big league game is about demonstrating -- and in turn, attempting to neutralize -- the sport's speediest specimens.

In the beginning, there was a car, parked on a baseball field, aiming a policeman's radar gun at a speeding fastball. Former National League outfielder Danny Litwhiler -- a renowned innovator who in 1942 was the first player to string together the fingers of his glove, resulting in the first error-free season by a full-time big leaguer -- had gotten the idea in the early 1970s while coaching at Michigan State. Seeing campus police pull cars over for speeding, Litwhiler wondered what would happen if he pointed the same radar guns at pitched baseballs. The devices, though, were powered through cars' cigarette lighters, so in order to test his theory, Litwhiler couldn't just sit behind the plate with a gun in hand. Hence the car on the field.
In truth, though, enterprising baseball minds had, for years, been trying to get a handle on the question of speed. There was the test conducted using the Remington Arms Company's machinery back in 1912, in which the ace hurler Walter Johnson fired a baseball into a machine used to track the speed of actual bullets. Similar tests through the years tracked fastballs using motorcycles, ballistic pendulums and slow-motion cameras, but nothing could offer the instantaneous and scalable utility of the police radar gun, which had been invented in 1954 to track speed using the Doppler effect.
Once Litwhiler's testing proved viable, he contacted JUGS Sports, which had been known for its pitching machines, and within several months, the coach had a battery-operated, portable prototype. Very quickly, the sport fell deep into a breathless state of radar love.
We now understand the science behind fastballs better than ever. In the 2016 documentary Fastball, Timothy Verstynen, a scientist at Carnegie Mellon, explains that a 90 mph fastball takes about 450 milliseconds to reach the plate. A 100 mph pitch gets there in 396 milliseconds. "That 50 some odd milliseconds is crucial brain time," he says. "Fifty milliseconds is an eternity in this kind of process. If you, as a rough estimate, assume that every snap to connection takes about two milliseconds, an extra 50 milliseconds or so gives you about 25 times the number of computations. So you get about 25 times the information just because you have that extra 50 milliseconds."
That's fine. But bear in mind that those 396 milliseconds are about equal to the time it takes you to blink. Batters have to rely on an optical illusion to have even a chance at connecting with a top-flight fastball. As demonstrated in a 2013 study at the University of California, Berkeley, the brain creates a simulation of where the ball will go, rather than identifying and capturing its present position. It "'pushes' forward moving objects so we perceive them as further along in their trajectory than the eye can see," wrote the study's researchers.
The study shines a light on a sport that's nearly perfect, and not in a campy, emotional sense. Truly, baseball players have, at this point, essentially mastered the art of controlling balls and bats, of positioning and directing throws, of cutting the quickest paths around the bases. We understand lineup construction better than we ever have before, and while fans and salty old-timers bemoan pitch counts and the like, we have nonetheless learned how to extend pitchers' careers. When it comes to baseball, there's little new under the sun, so the tweaks have to come around the margins, with measurements by the thousandth of a second.
Forty-five years after Litwhiler sparked our infatuation with metrics, baseball fans can now easily track every movement on the field. With dozens of cameras and sensors collecting data throughout the ballparks, there is barely any measurement out of reach. We know how far the balls travel, how fast they leave the bat, how much they spin out of the pitcher's hands. It's as if we've ditched the bunny ears and are finally seeing the game in high definition.
And different pitchers respond in different ways. Chad Green likes to look back every few pitches or so, to make sure that his fastball is around the speed he wants it to be - and he's usually even more interested in checking the velocity of his breaking pitches. Luis Severino tries not to look because he doesn't want to be discouraged by the number, or perhaps resort to overthrowing. And Carsten Sabathia, whose fastball barely flirts with 90 mph after it routinely reached speeds in the upper 90s when he was young? He has learned how to work the edges of the strike zone to generate soft contact, and so he insists that he never looks at the radar gun, and didn't even when he was throwing hard. But when he's a spectator, watching his teammates? Forget it. "Yeah," he acknowledges. "Every time."
And he's clearly not alone.

MLB has data for every pitch dating back to 2008, when the PITCHf/x system - the precursor to today's Statcast™ - became standard in all 30 parks. You can scour the lists to find the fastest deliveries since the tracking began, or you can just catch a glimpse at the underside of Chapman's left wrist, where "105.1 mph" is tattooed below a flame-tailed baseball. The closer has reached that mark twice in his big-league career: in 2010, as a member of the Cincinnati Reds, and with the Yankees on July 18, 2016, when he scaled that insane height against the Orioles' J.J. Hardy. "You can kind of tell when you're pitching," Chapman says, assisted by Yankees bilingual media relations coordinator Marlon Abreu. "It has a certain feel to it, when it feels like it's going faster."
It's hard to conceive just how fast 105.1 is. Big-league hitters can easily separate a 90 mph fastball from one coming in around 97. "Anything over 97, it's just fast," says Yankees catcher Austin Romine. "When you get over 101, that goes into WOW range." But that doesn't mean every 100 mph fastball is the same. "Different guys," says Aaron Judge, "have different spin rates on the ball. So for certain guys, 97 can play up and look like 100, 101. Pretty hard. And other guys, 97 will play down."

Beyond spin rate, though, there are any number of ways that a fastball can deceive. Maybe the hurler delivers with a smooth, fluid wind-up, giving the hitter a clear view of the ball the whole way. Another pitcher, though, might effectively hide a ball out of view, cutting down on the batter's time to identify the offering. All the while, the guys on the mound are actively working to disrupt the hitters, adding a mile here or subtracting one there, to say nothing of simple timing changes and unconventional pitch selection. They have no choice; as pitchers' velocities have been on the rise, the batters are adjusting. "We see so much stupid fast now, as far as numbers go," Greg Bird says, and Aaron Hicks suggests that he likes fastballs to come in as fast as possible.
At the plate, the batters engage in a delicate dance of timing and reacting. They need to have their bodies - and their brains - ready to connect to a ball they can barely see. "At 100 mph," Verstynen says in the documentary, "you're given almost no time to make a decision, and it's getting close to the range of where it's physiologically impossible to actually plan the voluntary action based off the information of the ball."
The velocity doesn't allow hitters to adjust to a fastball on the fly, so they must be ready for the fastest pitch they can imagine, and then react to anything offspeed. "He throws 95 to 97? Then I'm getting ready for 97 to 98, right down the middle, every single pitch," Judge says. "So my timing and my load is going to be ready, synced up. That pitch is going to be 97 right down the middle until it's not."
It's effective, then, to combat hitters' timing by throwing different looks at them. "We're not seven of the same exact guys," reliever Adam Warren says of his bullpen mates. "I'm throwing four different pitches at any time for strikes, whereas Dellin [Betances] is throwing 98 with a big hammer. Chappy is throwing a bunch of 105 mph heaters with a wipeout slider. It's so different, so hitters can't think, 'Oh, he's very similar to this guy.' You almost have to change your approach with each guy."
But when it's going well, all roads lead to Chapman delivering his otherworldly heat in the ninth inning. Since becoming a closer in 2012, he has recorded four seasons that rank in the top 10 all time for strikeouts per nine innings by a reliever. Nearly 40 percent of his pitches last year came in above 100 mph, and his average fastball velocity - an even 100.0 - ranked first in all of baseball. "It's all fast," Romine says of catching Chapman's heat. "If he's ahead in the count, it's going to be a little bit harder. If he's trying to punch someone out, it's probably going to be the best one he's got. If he's behind, he's probably just going to try to throw one in there 98. … If it's 0-2, 1-2, 2-2 and we've got a heater coming, he's trying to punch him out. And it's going to be hard.
"You can feel it. You can feel the difference."

As a catcher, Romine knows full well how big a role speed plays in the game -- and not just in the fastballs that explode into his glove. Once a runner gets on first, his whole mentality changes. "Guys that are fast, you have to be on your toes and ready to go, and you might have to sacrifice better receiving for being able to be ready to anticipate throwing and stuff like that," he says. "It's hard to be ready to throw him out and still be in a good position to steal a strike."
Like any good receiver, Romine can quote all the numbers that allow teams to control the running game. He knows that if the pitcher takes more than 1.5 seconds from the time he releases the ball to its contact with the catcher's mitt, then it will be almost impossible to cut down any potential base stealers. With elite runners able to swipe second in approximately 3 seconds, it would require a catcher to have a "pop time" - the duration between the "pops" of the catcher's and middle infielder's mitts - of 1.5 seconds. Yankees starting catcher Gary Sanchez is one of the best in the league at controlling the running game; last year, he finished third in the Majors with an average pop time of 1.93 seconds. You can see the problem.
But it's also up to the catcher to help keep the pitcher's focus on the batter, which is easier said than done when there's a speedy runner on first. "It almost adds a little bit of panic to you, just knowing that you've got a guy that might steal a base," Warren says. "You've got to focus more on the runner, which means less focus on the hitter." When the bases are empty or clogged by a slow runner, Warren adds, "You don't have to think about varying your looks, varying your times, picking off over there. You can just worry about executing your pitch and getting guys out."
Or, as Green puts it, when there's a runner on, "Everything is about trying to keep that guy on first base. It's definitely frustrating."
And elsewhere around the diamond? Outfielders need to know who's running, resetting the situation between every pitch. On a ball in the gap, their mental clock starts ticking right away, guiding their pacing and relay throws. First basemen need to hold runners on, be ready for pickoff throws from a pitcher or catcher, and still be in position to field batted balls.
Middle infielders might have the most going on, their roles constantly changing. "You assess the situation," Neil Walker says, describing his own series of mental calisthenics. "What inning, count, score? And then you assess who's running and who's hitting. Is it a possible hit-and-run situation? Is it a straight steal situation? And if it's a hit-and-run situation, and a fastball is thrown, and it's a right-handed hitter, you may switch the coverage. So you're looking at the signs because the signs will dictate who's covering. And once that responsibility is taken care of, then, out of the corner of your eye, you're keeping watch on the guy on first base to see if he takes off."
As with all defensive adjustments, there are trade-offs. Double-play depth sounds great when it leads to an easy twin-killing; when a hitter can deposit a ball in the enlarged hole between first and second base, though, the benefits aren't as apparent. So Bird prioritizes being ready to field his position at first base. With right-handed pitchers, who are less likely to pick runners off, he'll hold the guy on, but instead of straddling the base, he'll position himself a bit in front. "I always think, what would [the pitcher] rather have?" Bird says. "A 1 percent greater chance of picking a guy off? Or a double play? They want the double play. They want the [extra] out. For me, I'm there to catch the ball and tag the guy, but really, I'm there to play defense. Especially with a left-handed hitter up, I'm ready to go."
It's an on-field ballet, ever changing, ever determined to cut down the game's most frustrating and impressive characteristic: speed.

Video: Hurler of May: Aroldis Chapman
Way back in 1956, Lou "The Clocker" Miller charted the sport's fastest runners from home to first in an article for The Sporting News. At the time, Mickey Mantle was widely and correctly believed to be the Yankees' fastest player. "Right from my earliest boyhood," he once said, "I could run like a jackrabbit, and when I had most of my growth, about age 14, there was not a boy or man in town, and not too many rabbits, who could outrun me." Miller clocked the switch-hitting Mantle at 3.3 seconds from the left-hand side and 3.4 from the right. But Yogi Berra - nobody's idea of a speedster - measured in at 3.8, less than half a second slower. It's almost comical to try to process how fast the game moves.
Berra's assessment that "90 percent of the game is half mental" is regarded as a classic Yogi-ism, but what if he was right? What if the parts of the game that seem so purely athletic -- the speed, and the subsequent counters to it -- are actually as much mental as physical? Would it be wrong to suggest that the balance could occupy as much as 90 percent of the game?
Flash back to that showdown between Chapman and Kinsler. Even Chapman, the fastest pitcher in Major League history, knows that he can't get by on speed alone. "Depending on the pitch, depending on the batter, depending on the count, as a pitcher, you want to be able to mix in certain situations," he says. "You can't use the same pitch, same location, same velocity all the time. You've got to be able to mix it. And that mix, it includes location, velocity, type of pitch, sequence and so on and so on."
As Kinsler stands in the box that night in Anaheim, with the tying run on second base and a 1-2 count, he is finishing up a month that has seen him make contact on just a tick under 95 percent of his swings -- one of the highest contact rates of any hitter in the league with at least 70 at-bats. He has just seen four straight 101 mph pitches. So what does the velocity king, baseball's ultimate speed demon, do next?
Chapman reaches back and flings an 87 mph slider, directly over the middle of the plate, dead-center in the strike zone. Unlike his superhuman heater, it is a pitch any ordinary big leaguer can throw. Kinsler swings through it, helplessly. The Yankees win, running their win streak to nine in a row.
The fastest fastball? Chapman's got that. But to make it work, he still needs to win the game that's usually at least half mental.