SARASOTA, Fla. -- Standing in the bullpen in Aberdeen, Maryland, that day, the kid on the mound had no idea that he was about to stumble onto a pitch that would draw comparisons to the great Mariano Rivera. All Zach Britton was doing was trying to figure out how to throw your basic, all-American cutter.

It was 2007. He was 19 years old. His ERA was climbing. And the future closer for the Baltimore Orioles wasn't even sure he wanted to pitch for a living.

But then it happened.

He threw a pitch that was supposed to zig left, like cutters are supposed to zig. Instead, it didn't merely zag right. It plummeted toward earth as if he'd just dropped a boulder off a bridge. It was a life-changing moment.

But how was the guy who threw it supposed to know that? All it felt like was yet one more pitch he couldn't master.

"He said, 'The ball's supposed to go the other way,'" Britton's pitching coach at Class A Aberdeen, Calvin Maduro, recalls. "He was like, 'The ball's sinking -- not cutting.' I said, 'Man, keep that.'"

Keep what? It's one thing to throw one pitch that does something totally unexpected. But could Britton defy the laws of physics and make it move that way twice?

"We did it for maybe 10 minutes," Maduro says. "It just kept happening."

It just kept happening, all right. For a decade. Ten years later, Zach Britton is still holding the most unique pitch in baseball all wrong -- and riding it to places no relief pitcher has ever gone.

Shades of Mariano

Orioles closer Zach Britton posted a 0.54 ERA in 2016 by throwing a single devastating pitch 92 percent of the time. Sound familiar? Amazingly, Britton stumbled upon the unhittable sinker that has made him a star. Elsa/Getty Images

Which is more amazing: that America's foremost ground ball machine is coming off a season in which he had a 0.54 ERA, the lowest by any relief pitcher in history with 50 or more innings, or that he did so by throwing just that one pitch, the man-eating sinker, 92 percent of the time?

Ask his manager if it's possible that his closer could be even better this season, and Buck Showalter snaps: "No. Not even possible." He thinks he just witnessed "the best year by a relief pitcher ever."

But ask the manager if he thinks Britton needs to vary his patterns so he doesn't have to rely on the same pitch 92 percent of the time, and Showalter cocks his head to give That Look.

"Right now, he can do whatever he did last year," Showalter says. "And I'm OK with that."

Doesn't logic say that what Zach Britton does shouldn't be possible? How can any pitcher have a pitch so unhittable that he can haul it out pretty much every time he throws a baseball and have a 0.54 ERA to show for it -- in the AL East?

"I don't remember anything like that," Britton's bullpen amigo, Darren O'Day, says, "except for No. 42 in pinstripes."

No. 42 in pinstripes, of course, was a fellow named Mariano. He got slightly famous for firing cutter after cutter after cutter. For 19 seasons. That's going to lead him to Cooperstown someday. So it isn't that there's no precedent for a guy spinning the same darned pitch all night and still shaking hands a lot.

But when Britton hears his name in the same sentence as the Great Mariano, his eyes spin, almost in embarrassment.

"Wow," he says. "That's pretty tough company to keep, right?"

"Just do this for another 18 years," someone says.

"You know, I try not to think of it that way," Britton replies. "I think he's a good reference point, though."

"We should make him go back a couple of steps and maybe grip the ball a little bit different, so we can have a chance."

Rivera is a better reference point than you'd think. Over the past eight seasons, ESPN Stats & Info could find only two pitchers who threw any pitch, in any full season, as much as 92 percent of the time. One was Britton in 2016. The other was Rivera in 2009, when 92.9 percent of the pitches he threw were cutters. Somehow, it worked out OK for both of them.

But there was a long time, Britton admits, when even he didn't think it was a good idea to throw his best pitch that often. Then his former pitching coaches, Dave Wallace and Dom Chiti, convinced him otherwise.

"I felt like I couldn't throw that pitch 90 percent of the time," Britton says. "I thought I needed to mix in something else. Otherwise, I was going to get too predictable. And their whole philosophy behind that was: Does it really matter if they know what's coming if you execute the pitch you want to?"

Britton went from featuring the sinker about 67 percent of the time in 2013 to more than 90 percent in each of the past three seasons. The results were mind-blowing. He allowed just 32 balls in the air all of the past season. Even the hitters don't understand how that can happen.

"It's kind of a different at-bat because you know exactly what you're going to get," says Tampa Bay's Steven Souza, who is 1-for-6 against Britton, with three strikeouts and (what else?) a ground ball single. "And still he finds a way to make you look kind of foolish sometimes. It's something I can't explain, really.

"We should make him go back a couple of steps and maybe grip the ball a little bit different, so we can have a chance."

Ground control

Who has the better ground game: Zach Britton or Ezekiel Elliott? Britton's 80.2 percent ground ball rate last year wasn't just great. It was historic. Data on ground ball percentage goes back only about three decades, but what other pitchers in that time induced that high a percentage of ground balls over that many innings? None.

Shaun Marcum once got 13 fly ball outs in relief in one game (in 2013). Britton just allowed 13 fly balls all season. Incredibly, that comes to one every other week. You can tell it's a rarity if even the guy on the mound admits that he gets disoriented when somebody manages to hit one in the air.

"There was a stretch last year," he says, chuckling, "where I hadn't given one up in a while, and I remember a guy flew out, I think, to [Mark] Trumbo, and I was kind of searching in the air for it. Matt Wieters came up to me after the game and said, 'What were you doing?' And I was like, 'He swung, and I was looking on the ground. And then I looked up, and Trumbo was catching it in the air.'"

How does he do it?

What's the secret to baseball's most devastating pitch? Even other pitchers can't figure it out.

"Anybody who comes in contact with Zach has asked, 'Hey, how do you throw that? I'd like to try it,'" O'Day says. "But it doesn't work for anybody else."

What's O'Day's best theory for why that is?

"You see how short his arms are?" Britton's setup man jokes. "The guy can't reach the bottom of his pockets. There's something funny going on."

In truth, it's all in the grip and the wrist. Britton wasn't permitted by the proper authorities (i.e. his manager) to demonstrate the grip in public. But he tried to explain it.

"It's pretty similar to a traditional curveball," he says. "You're holding that one seam. When I show people, they say, 'Oh, that's how I hold my curveball.' ... But rather than turn it over, I'm just keeping my hand back behind the ball and trying to drive it down through the catcher."

"You see how short his arms are? The guy can't reach the bottom of his pockets. There's something funny going on."

At 96 mph, that pitch is exploding on the hitter much faster than a curveball or cutter would. Then it drops through an invisible trap door. Meanwhile, hitters can never be certain if the next sinker will move the same as the one they just whiffed on. They should know the guy throwing it isn't always sure, either.

"I'm still trying to figure out sometimes, when it goes a certain way, how I can know when it's going to happen," Britton says. "I feel like it's three different pitches in one sometimes."

There is one that "goes straight down" and a second version that "will run away from a right-handed hitter" and a third that sometimes cuts -- just not necessarily on purpose. Britton has figured out the first two. But the third "is one I'm still trying to keep in my back pocket," he says, "and use that one and know what's going to happen."

"I'm sure," he says, with another laugh, "the catchers would like that."

Rinse and repeat?

What does a fellow do for an encore after he just had the greatest season in relief pitching history? Hey, good luck, because no matter what column you looked at on the stat sheet, Britton was putting up numbers last year that don't seem doable on a PlayStation.

Leadoff hitters got three hits off him all season (3-for-24). No. 3 hitters batted .111 (2-for-18). Cleanup men went 5-for-28 (.179) with one extra-base hit. He faced 26 hitters with a runner on third -- and gave up one hit. With men in scoring position, the opposition went 5-for-59 (.085), with zero extra-base hits. How unhittable could one man be?

Since the dawn of the modern save rule, no relief pitcher has had an ERA lower than 1.00 in consecutive full seasons. Only Wade Davis (1.00 in 2014, 0.94 in 2015) came close.

For the record, the best back-to-back seasons of Rivera's career were 2008 and 2009, when his ERA was 1.40 and 1.76, respectively. But the 2016 winner of the Mariano Rivera Award gladly sought him out for advice anyway.

"I had the chance to talk to him at the World Series game when I got the Rivera Award," Britton says. "Kinda just picked his brain a little bit. He just told me: 'Command. No matter what you do, always work on commanding it, because at the end of the day ... you've got to be able to command it to sustain success.'"

In a spring in which he has been able to pitch only sparingly because of an oblique issue, Britton has worked mostly to recapture his feel of the pitch that got him this far. After years of honing it, he now feels "it's just kind of part of who I am. So when I pick up a baseball, I find that grip."

Who could have imagined, when Britton stood on that mound in Aberdeen 10 years ago messing with a cutter, that it could have led him to this? Not the guy who taught him this career-altering pitch -- by accident.

"No, no, no, no, no," Calvin Maduro says. "I just knew at that time that that thing was nasty, and it was going to the other way from where it was supposed to be going. But I never thought it would be like that. And I'm sure he never thought it would be like that, either."