Riley O'Brien

Riley O’Brien is a right-handed relief pitcher whose pro path began after he was selected in the 8th round (pick 4) of the 2017 MLB Draft. Born February 6, 1995, in Seattle, Washington, he attended Shorewood High School and played college baseball at the College of Idaho. He made his MLB debut on September 28, 2021. In 2025 with St. Louis, O’Brien worked 48.0 innings across 42 relief appearances, posting a 2.063 ERA with a 1.1458 WHIP and 45 strikeouts. Opponents hit .196 against him with a .313 on-base percentage and .274 slugging, and his home-run rate was 0.375 HR/9. He logged nine save opportunities, recording six saves and six holds, with three blown saves. In the 2026 regular season to date, his bullpen line includes 35.1 innings over 35 games with a 3.821 ERA, 1.1604 WHIP, and 21 saves in 25 save chances. His strikeout rate sat at 8.66 K/9 with a 3.09 K/BB ratio, while limiting opponents to a .231 batting average against. Pitch data shows a power sinker averaging 98.2 mph (max 101.1) and an overall average pitch velocity of 93.1 mph, with a 3.235 groundball-to-flyball ratio.