Mason Miller is already throwing triple-digit heat in the majors after a short stay in Las Vegas.

Miller — the No. 3-ranked prospect in the Oakland Athletics organization, according to MLB.com — was promoted to join the MLB club Tuesday and made his first start Wednesday against the Chicago Cubs.

Miller went 4⅓ innings in his MLB debut, allowing four hits, two earned runs and a walk while striking out five in the A’s 12-2 loss. He topped 100 mph on 15 pitches, MLB.com reported, with a high of 102.5.

The call-up caps a meteoric rise for Miller, who was selected by the A’s in the third round of the 2021 draft. The 24-year-old right-hander has appeared in only 11 games in the minor leagues and just three games at the Triple-A level, becoming the first member of the A’s 2021 draft class to make his MLB debut.

Miller began this season at Double-A Midland after rising all the way from the rookie league to Triple-A in 2022. He was promoted to the Aviators after one start with the RockHounds. In his lone Triple-A start this season, Miller went five innings, allowing no hits, runs or walks while striking out 11 against Salt Lake on Friday.

Miller had 19 strikeouts in 8⅔ innings of minor league work this season.

The Pittsburgh native spent four seasons at Waynesburg University, a Division III school in Pennsylvania. Miller transferred to Gardner-Webb for his final season, where he impressed enough to become a third-round pick.

He joins a roster whose pitchers have struggled this season. Entering Wednesday, the A’s pitching staff had an MLB-worst 7.47 ERA.

Contact reporter Andy Yamashita at [email protected]. Follow @ANYamashita on Twitter.