Aroldis Chapman made history in the 2015 All-Star Game by firing a 103.4 mph fastball by Mike Moustakas to set the record for fastest pitch in a Midsummer Classic. Since then, only Ryan Helsley -- who fired a pair of 103 mph fastballs in 2022 -- has come close to touching that mark.

With Mason Miller heading to the 2024 All-Star Game, Chapman’s record might have its most formidable challenger yet.

Miller has emerged as the most electrifying closer in baseball. The flamethrowing A’s rookie has struck out nearly half of his batters faced (46.6 percent strikeout rate), with his 68 strikeouts leading all Major League relievers.

While Miller’s wipeout slider is as filthy as they come, and he’s also tinkered with integrating a “splinker” into his arsenal, his fastball is truly one of the elite pitches in the game. Triple-digit velocities are his specialty. Miller has thrown a whopping 286 pitches of at least 100 mph or harder, by far the most in MLB. The average velocity of 100.9 mph on Miller’s heater is also the highest of any pitcher in the Majors.

So, could Miller be the one to surpass Chapman this year? He was unaware of the record until learning about it during a series between the A’s and Red Sox at Fenway Park last week. Upon hearing the number, Miller quickly pointed out that his fastest pitch thrown this season -- a 103.7 mph fastball to Wyatt Langford of the Rangers on April 11 -- came at Globe Life Field, which happens to be the site of this year’s All-Star Game.

“I got 103.7 in [Texas] earlier in the year,” said Miller, who has thrown five pitches tracked at 103.0 mph or faster this season. “I don’t know. Now you threw it out there, so I’m going to be thinking about it. We’ll see. I’m not going to go too crazy. I don’t want to hit anybody or anything like that.”

Miller should not worry too much about hitting someone. He’s gone without hitting any of his first 146 batters faced this year. It’s that ability to control the fastball that separates him from the average hard-throwing pitcher.

“There’s no one like him,” A’s catcher Shea Langeliers said of Miller. “He’s got some of the best stuff I’ve ever caught or seen in my life. He’s next-level. ... Just a really, really special pitcher.”

The rise of Miller’s dominance has been a national storyline this season that quickly accelerated following a visit to MLB Network and recognition as American League Reliever of the Month for March/April. The newfound fame is something he never could have imagined six years ago, when he was diagnosed with Type 1 juvenile diabetes while a sophomore at Division III Waynesburg University.

The journey has been well documented. Miller found the right diet and strength training program, bulked up to 220 pounds and increased his fastball velocity from 87-88 mph to as high as 99 mph, leading to the A’s selecting him in the third round of the 2021 MLB Draft.

Even if Miller allowed himself to think an All-Star Game was in his future, he would have figured it would come as a starting pitcher. Starting is all he’d done for the majority of his career before this season.

This past offseason, A’s manager Mark Kotsay and general manager David Forst met with Miller to discuss a move to the bullpen as a means of preserving the health of his tantalizing arm after a UCL sprain in his right elbow sidelined him for nearly four months in 2023.

“I pride myself on accepting the role that the team needs me to do,” Miller said. “Getting that call and talking to Kots about it, understanding the thought process, it was pretty easy for me to get on board.”

Miller has made the transition from starting to closing appear seamless. He has mastered the art of handling the pressure of the ninth inning by leaning into those nerves to bring out the best in him.

While the A’s have left the door open for Miller to return to starting in the future, his massive success as a closer is enough even for him to believe this might just be his best role for the long-term.

“My body feels good right now,” Miller said. “With the success I’ve had and given my health history, right now our need is in the bullpen. ... I feel good and I like doing it.”