OAKLAND >> Mason Miller is bringing his 100-mph-plus fastball to baseball’s All-Star Game, doing so as the Athletics’ lone representative — and perhaps their last as an Oakland-based ballclub.

“I’m super excited. It’s what every player works for,” Miller said Sunday, as the A’s closed their homestand against the Baltimore Orioles. “To have the success I’ve had in a new role this year, and to be able to represent our guys, it’s really an honor.”

Miller wasn’t otherwise summoned Sunday as the A’s lost 6-3 to the Baltimore Orioles in front of 14,524 at the Coliseum, closing out a 4-2 homestand and their last before next week’s All-Star break.

Miller’s conversion to a fireball-throwing closer has highlighted the A’s up-and-down-and-out season, before they leave for a three-season layover in Sacramento and planned relocation to Las Vegas.

“Regardless of everything else that surrounds the team, we’re still big-leaguers,” Miller added. “We still are putting in the work and effort every day to make ourselves the most competitive team we can be.”

Miller’s velocity and excellence for a 34-57 team make him an alluring attraction for the July 16 Midsummer Classic in Arlington, Texas. He entered Sunday’s All-Star selection with a majors-leading 278 pitches of 100-mph or greater; no one else has more than 176 such pitches. His 66 strikeouts (37 2/3 innings) are the most among all relievers, and his 14 saves lead all rookies; the A’s rookie record of 26 saves was set by Andrew Bailey, their last rookie All-Star (2019).

Miller thus joins 68 other players who’ve represented the A’s since their 1968 move to Oakland from Kansas City. Actually, he won’t be alone in an Athletics uniform. A’s manager Mark Kotsay will serve as a coach on American League manager Bruce Bochy’s staff.

Miller hopes an injury-replacement spot could open up for red-hot slugger Brent Rooker, last year’s A’s All-Star who leads them with 18 home runs this season. “He’s a guy you want to have that honor as well, because he’s certainly earned it,” Miller said. (Houston’s Yordan Alvarez is the American League’s starter at designated hitter; he did not play Sunday, and he left Saturday’s game after being hit on the knee.)

Although the initial All-Star rosters were revealed on ESPN during Sunday’s game, Miller got the word pregame from Kotsay. At the same time, the greatest closers in A’s history, Dennis Eckersley and Rollie Fingers, were at the Coliseum. Fans received Fingers bobblehead dolls, and he later threw out the ceremonial first pitch to fellow Hall of Famer Eckersley.

How Miller followed in their starter-to-closer footsteps was a “really surreal” journey. In 10 games last year, he went 0-3 with a 3.78 ERA. Miller liked what he heard from Kotsay about switching to the closer role this year.

“Talking to Kots about it, understanding the thought process, it was pretty easy to get on board with it,” Miller said. “Then it was about making the physical adjustments and the day-in, day-out wear of a bullpen, as opposed to every fifth day (as a starter).”

“I see him being around a while, if he can stay healthy,” Fingers said of Miller on NBC Sports Bay Area’s pregame show. “He does throw hard. He has nasty stuff. I don’t think I’d want to face him. He’s going to be around a while as a closer. He has the type of arm he can throw two or three ballgames in a row.”

Miller, who turns 26 on Aug. 24, surely could be sought in a trade for another team’s bullpen. For now, he’s priding himself on fulfilling the A’s needs, like he did on the New York Yankees’ off-Broadway stage, where he struck out Anthony Volpe, Juan Soto and Aaron Judge in a 1-2-3 ninth for an April 22 save.

“To do that against the top of the order was really awesome for me, as still a young, bullpen, closer-type guy,” Miller recalled.

Shortly after the A’s drafted him in the 2021 third round, Miller first saw his fastball clock 100 mph three years ago at the Athletics’ Arizona complex. “At Gardner-Webb (University), we said that I did (hit 100 mph), but I didn’t get to see it myself,” noted Miller.

Miller transferred there after four years at Waynesburg University in his native Pennsylvania. During those early college years, Miller learned he had Type I diabeties.

“It feels like a lifetime ago, honestly,” Miller said. “Taking the time in moments like this to reflect on where I’ve been and all the steps.”