What years did Riley O'Brien play?

Riley O'Brien played in Major League Baseball from 2021 to 2026.

Was Riley O'Brien a pitcher?

Yes. Riley O'Brien pitched in the major leagues, recording 6 wins and 116 strikeouts.

What was Riley O'Brien's career ERA?

Riley O'Brien finished with a 3.79 career ERA, going 6-9 with 116 strikeouts.

How many strikeouts did Riley O'Brien have?

Riley O'Brien recorded 116 career strikeouts.

Is Riley O'Brien in the Hall of Fame?

No. Riley O'Brien has not been inducted into the National Baseball Hall of Fame.

What teams did Riley O'Brien play for?

Riley O'Brien played for the Cincinnati Reds, the Seattle Mariners, the St. Louis Cardinals, and the St. Louis Cardinals.

Riley O'Brien

Pitcher · Career Stats, Bio & Records (2021-2026)

Riley O'Brien is a pitcher who has played in Major League Baseball since 2021 for 4 teams, including the Cincinnati Reds, a span of 6 seasons. Across 112 career appearances, he has gone 6-9 with a 3.79 ERA, 116 strikeouts, and 42 saves. His career Pitcher PIV — Baseball Data Hub's era-adjusted measure of pitching impact — is 659.5.

W (Wins):: Games credited to a pitcher whose team took a lead it never surrendered while he was the pitcher of record.
ERA (Earned Run Average):: Earned runs allowed per nine innings pitched: (ER × 9) ÷ IP. The primary measure of pitching effectiveness.
SO (Strikeouts):: For a batter, times retired on a third strike; for a pitcher, batters retired on a third strike.
WHIP (Walks and Hits per Inning Pitched):: Baserunners allowed per inning: (BB + H) ÷ IP. Under 1.00 is elite.

Data updated September 9, 2026

Active Player

W–L 6–9

ERA 3.79

WHIP 1.35

SO 116

Pitcher PIV 659.5

Position: Pitcher
Bats / Throws: R / R
Height / Weight: 6'4" / 180 lb
Born: 2/6/1995 in Seattle, WA, USA
MLB Debut: 2021-09-28

Full name: Riley Chun-Young O'Brien

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Career Pitching Statistics

Riley O'Brien — Career Pitching Statistics
W	L	G	GS	CG	SHO	SV	IP	H	ER	HR	BB	SO	ERA	Pitcher PIV
6	9	112	1	0	0	42	116.3	97	49	9	60	116	3.79	659.5

Career ERA 3.79 vs. league average 4.13 across their career seasons — 8.2% better than league average.

Season-by-Season Pitching

Pitching Career Arc

Click a stat to plot it across every season.

Riley O'Brien — Season-by-Season Pitching
Year	Team	Lg	W	L	G	GS	SV	IP	H	ER	BB	SO	ERA	Lg ERA	Pitcher PIV
2021	CIN	NL	0	1	1	1	0	1.3	2	2	3	2	13.50	—	0.0
2022	SEA	AL	0	0	1	0	0	1.0	1	0	1	1	0.00	—	0.0
2024	SLN	NL	0	0	8	0	0	8.0	13	10	8	11	11.25	—	0.0
2025	SLN	NL	3	1	42	0	6	48.0	33	11	22	45	2.06	4.16 (+50%)	659.5
2026	STL	NL	3	7	60	0	36	58.0	48	26	26	57	4.03	4.17 (+3%)	-
Career · 5 seasons			6	9	112	1	42	116.1	97	49	60	116	3.79	—	659

Lg columns show the league average for that season, with the player's figure as a percentage above or below it. Career totals the seasons listed above.

Career Batting Statistics

Riley O'Brien — Career Batting Statistics
G	AB	R	H	2B	3B	HR	RBI	SB	BB	SO	AVG	OBP	SLG	OPS	PIV
52	0	0	0	0	0	0	0	0	0	0	.000	.000	.000	.000	0

Season-by-Season Batting

Career Arc

Click a stat to plot it across every season.

Riley O'Brien — Season-by-Season Batting
Year	Team	Lg	G	AVG	Lg AVG	Lg OBP	Lg SLG	Lg OPS	PIV
2021	CIN	NL	1	.000	—	—	—	—	0.0
2022	SEA	AL	1	.000	—	—	—	—	0.0
2024	SLN	NL	8	.000	—	—	—	—	0.0
2025	SLN	NL	42	.000	—	—	—	—	0.0
Career · 4 seasons			52	—	—	—	—	—	0

Lg columns show the league average for that season, with the player's figure as a percentage above or below it. Career totals the seasons listed above.

Game Log & Splits

View full game log (104 games) →

Per-game data from Retrosheet (regular season, through 2025).

Batting — Home / Away

Riley O'Brien — Batting — Home / Away
Split	G	AB	R	H	HR	RBI	AVG
Home	27	0	0	0	0	0	—
Away	25	0	0	0	0	0	—

Pitching — Home / Away

Riley O'Brien — Pitching — Home / Away
Split	G	IP	H	ER	BB	SO	ERA
Home	27	31.1	19	3	11	24	0.86
Away	25	27.0	30	20	23	35	6.67

Last 10 Games — Pitching

Riley O'Brien — Last 10 Games — Pitching
Date	Tm	Opp	Dec	IP	H	R	ER	BB	SO
2025-09-28	STL	CHC	—	1.0	1	0	0	0	2
2025-09-24	STL	SFG	L	1.0	2	1	1	1	0
2025-09-23	STL	SFG	SV	0.1	0	0	0	0	1
2025-09-21	STL	MIL	—	1.0	0	0	0	0	0
2025-09-20	STL	MIL	—	1.1	0	0	0	1	1
2025-09-16	STL	CIN	SV	1.0	0	0	0	0	1
2025-09-14	STL	MIL	SV	1.0	0	0	0	1	2
2025-09-13	STL	MIL	—	0.0	2	3	3	0	0
2025-09-10	STL	SEA	—	2.0	2	1	0	2	2
2025-09-07	STL	SFG	SV	1.0	1	0	0	0	0

Fielding Statistics

Career Fielding Totals by Position

Riley O'Brien — Career Fielding Totals by Position
Position	G	GS	PO	A	E	DP
P	52	1	5	8	0	1

Season-by-Season Fielding

Riley O'Brien — Season-by-Season Fielding
Year	Team	Pos	G	GS	PO	A	DP
2021	CIN	P	1	1	0	0	0
2022	SEA	P	1	0	0	0	0
2024	SLN	P	8	0	0	0	0
2025	SLN	P	42	0	5	8	1

Career Games by Position

Position Diamond

Circle size = games played at each position.

Riley O'Brien — Career Games by Position
Position	Games
Pitcher	52

Frequently Asked Questions about Riley O'Brien

What years did Riley O'Brien play?: Riley O'Brien played in Major League Baseball from 2021 to 2026.
Was Riley O'Brien a pitcher?: Yes. Riley O'Brien pitched in the major leagues, recording 6 wins and 116 strikeouts.
What was Riley O'Brien's career ERA?: Riley O'Brien finished with a 3.79 career ERA, going 6-9 with 116 strikeouts.
How many strikeouts did Riley O'Brien have?: Riley O'Brien recorded 116 career strikeouts.
Is Riley O'Brien in the Hall of Fame?: No. Riley O'Brien has not been inducted into the National Baseball Hall of Fame.
What teams did Riley O'Brien play for?: Riley O'Brien played for the Cincinnati Reds, the Seattle Mariners, the St. Louis Cardinals, and the St. Louis Cardinals.