OAKLAND -- Mason Miller is one of the quieter, milder players inside the A's clubhouse.
So when he hopped off the Coliseum mound, unleashing a roar and fist pumping in the air after firing a nasty slider that Connor Wong flailed at for strike three, the reaction caught manager Mark Kotsay off guard.
"You saw the emotion from Mason," Kotsay said. "That was awesome."
Miller, who recently graduated off Oakland's Top 30 Prospects list as its top overall pitching prospect, finally experienced the closer-type situation the A's had been looking to get him. Despite ultimately falling to the Red Sox, 5-4, in 11 innings on Tuesday night, they were kept in the game by Miller's dazzling effort. The Wong strikeout that ended the 10th inning punctuated a dominant two scoreless innings with four strikeouts.
With Miller shifting to a bullpen role this season to preserve his health by limiting his innings, the A's envision the flamethrower emerging as their closer in 2024. After his first outing came in a blowout loss, Tuesday was his first taste of the high-stakes drama that comes with such a role.
"You can't simulate that kind of adrenaline," Miller said. "I was excited to be in that spot where the game is on the line. It's an opportunity to finish what everybody else has worked hard for. It's an opportunity I'm excited to get back in."
Facing the heart of Boston's order as he took over in the ninth, Miller began the frame with back-to-back strikeouts of Tyler O'Neill and Rafael Devers, both swinging on high-80s sliders, before ending the inning on a flyout. In the 10th, Miller also fanned Wilyer Abreu, swinging on a 101.8 mph fastball.
This is why the A's believe Miller can thrive as a closer.
His high-octane fastball, coupled with a devastating wipeout slider, can make life miserable for opposing hitters. During Wong's 10th-inning strikeout, the putaway slider was preceded by a 100.5 mph fastball, providing quite the variation in speeds.
One pitch before that 100.5 mph heater, Miller uncorked a 102.4 mph fastball that qualified as the fastest pitch by any pitcher so far in the 2024 season. In fact, Miller's five fastest pitches of the night, ranging from 101.4-102.4 mph, register as the five fastest pitches of the season.
"He's a special arm," said A's starting pitcher Alex Wood, who took a no-decision after allowing three runs on six hits and two walks with seven strikeouts in five innings. "It's not just his heater. His slider is a real weapon. It was fun to see him come in. You saw some energy out of him. It's fun when you see a little bit of the dog come out in the moment. He's a quiet, reserved kid. To see him get fired up there, it was a cool moment."
Miller generated 14 swings and 11 whiffs on his 29 pitches. The fastball averaged 100.8 mph, maxed out at 102.4 mph and registered at 100 mph or faster eight times.
The A's have yet to find themselves in a save situation this season.
Once they do, Miller is expected to get the first crack. It's something he prepared for all Spring Training, and Tuesday's performance showed why he's ready for the task.
"I'm very comfortable in it," Miller said. "The mental side of it is the harder part. You're locked in every day. There's certain days where you're ready to get in there and you don't. … That's the challenge."
After an error-filled start to the season, Tuesday's loss provided a positive in that it was Oakland's first game without an error after committing 13 through the first five. That sound defense, along with two-run homers by JJ Bleday and Shea Langeliers, led to a much more competitive ballgame for the A's, who nearly tied the game in the 11th on a deep drive to center by Langeliers that instead resulted in a spectacular catch on the run by Ceddanne Rafaela.
"This [game] kind of hurts," Kotsay said. "But these guys bounced back from last night and put that game behind them. … We fell short. But it was a good baseball game. All around, a much better performance tonight."