[3] Kris was a pitcher who spent several seasons in the St. Louis Cardinals' minor league system and was with the Triple-A Memphis Redbirds at the time of Reid's birth.

Following the season, Detmers' family moved to Chatham, Illinois, after his mother started a new job and he transferred to Glenwood High School for his senior year.

[9][10] After graduating high school and forgoing his late-round 2017 draft selection, Detmers honored his commitment to play college baseball for the Louisville Cardinals.

[15] He finished the season with 2.78 ERA and 167 strikeouts in 113+1⁄3 innings and tied the school record for wins in a season with 13 to four losses and was named the Atlantic Coast Conference's (ACC) Pitcher of the Year, first-team All-ACC, a first-team All-American by the American Baseball Coaches Association and the National Collegiate Baseball Writers Association.

[19] Detmers entered his junior season on the watch list for the Golden Spikes Award and as a top prospect for the 2020 Major League Baseball draft.

[34] During spring training in 2022, Angels manager Joe Maddon announced that Detmers had beat out Jaime Barría for the team's sixth starting rotation spot.

[35] His turn in the rotation was moved up to the Angels' second game on April 8 against the Houston Astros when Patrick Sandoval missed his scheduled start.

[36] On May 10, 2022, Detmers pitched the 12th no-hitter in Angels history, recording two strikeouts and one walk against the Tampa Bay Rays in his 11th major league start.

[38] During his time with Salt Lake, minor league pitching instructor Buddy Carlyle noticed an issue with Detmers's mechanics during a 15-minute film session and helped him correct it.

[42] Detmers followed Sandy Koufax and Mike Fiers as the third player in MLB history to throw a no-hitter and an immaculate inning in the same season, and was the first to do so as a rookie.

[43] Detmers was placed fourth in the Angels' starting rotation for the 2023 season, behind Shohei Ohtani, Patrick Sandoval, and free agent signee Tyler Anderson.

[46][47] Detmers threw quality starts against the Chicago White Sox and Arizona Diamondbacks in his next two outings but then posted an 0–4 record with a 10.30 ERA across 25+1⁄3 innings pitched in six games from July 8 to August 11.

[45] On August 16, during a game against the division-leading Texas Rangers at Globe Life Field, he carried another no-hit bid into the 8th inning before surrendering a hit to Marcus Semien with one out.

[54] As a prospect, MLB Pipeline scouts graded Detmers's fastball at 55, slider at 50, curveball at 60, changeup at 50, control at 55, and overall profile at 55 on the site's 20–80 scale.

[55] Following a mechanics adjustment during a minor league stint in July 2022, Detmers saw improved results with his slider and began using it as his strikeout pitch.