Players · O · Pitcher · 2026

Riley O'Brien

St. Louis Cardinals National League Central

Age: 31
B/T: R/R
Height: 6' 4"
Weight: 180 lb
Number: #61

Born: February 6, 1995 in Seattle, WA, United States
MLB debut: September 28, 2021
Drafted: 2017, round 8
College: College of Idaho

dbWAR: .5
IP: 64.0
ERA: 4.08
FIP: 3.95
K/9: 9.0
FIP−: 94

Riley O'Brien is a relief pitcher for the St. Louis Cardinals. In 2026 he struck out 64 batters over 64.0 innings across 66 appearances, going 3-9. His ERA of 4.08 is 2.4% lower than the league average of 4.18 — 11th of 16 on his team, and 278th of 538 among MLB pitchers with 20+ innings. Stripping out defence, his 3.95 FIP suggests the ERA was no fluke. He missed bats on 26.6% of swings (11.7% of every pitch he threw), walked 10.5% of the batters he faced and struck out 23.2%. His 0.5 dbWAR is built from that FIP rather than runs allowed, so it credits him for what he controls and not for the defence behind him.

League context

Percentile among qualified pitchers, 2026.

FIP3.95

K/99.0

WHIP1.28

WAR.5

WAR by season

Pitching

Standard and advanced, by season.


2026	STL	66	0	64.0	3	9	38	53	29	64	29	4.08	3.95	1.28	9.0	4.1	98	94	0.5
2025	STL	42	0	48.0	3	1	6	33	11	45	22	2.06	3.61	1.15	8.4	4.1	50	87	0.6
2024	STL	8	0	8.0	0	0	0	13	10	11	8	11.25	7.04	2.63	12.4	9.0	276	173	-0.2
2022	SEA	1	0	1.0	0	0	0	1	0	1	1	0.00	4.11	2.00	9.0	9.0	0	104	0.0
2021	CIN	1	1	1.1	0	1	0	2	2	2	3	13.50	26.42	3.75	13.5	20.3	316	619	-0.3

Platoon splits

How left- and right-handed hitters fare against him.

Season

Opponent batting by the side the hitter bats from, 2026. Counted from play-by-play, so totals can differ from the box-score season line by a plate appearance or two.
Split	PA	AB	H	HR	BB	SO	AVG	OBP	SLG	wOBA	K%
vs LHB	150	123	30	3	19	29	.244	.369	.350	.324	19.3%
vs RHB	126	110	23	2	10	35	.209	.298	.318	.284	27.8%

Pitch sequencing

What Riley O'Brien throws in each count, and what he follows each pitch with. Select any cell for the breakdown.

ShowBatter

SinkerSweeperSliderChangeup

Select a count to see exactly what Riley O'Brien throws in it.

Pitch arsenal

What he throws, how hard, how often it misses, and what hitters do with it.

Season


Sinker	58.4%	621	97.7	2,197	48.0%	16.4%	147	.279	.753
Sweeper	32.8%	349	82.9	2,318	42.1%	47.2%	65	.138	.497
Slider	7.7%	82	90.6	2,444	43.9%	21.4%	22	.136	.549
Changeup	1.1%	12	91.0	1,903	41.7%	66.7%	0	—	—

Riley O'Brien's arsenal by usage. Velocity is average release speed in mph, spin in rpm, and whiff rate is misses per swing — the cleanest single measure of whether a pitch beats hitters. BAA and OPS are what hitters did against each pitch, credited to the one that ended the plate appearance, and are left blank under 15 at-bats.

Head to head

Put Riley O'Brien beside up to three others.

Compare — add up to 3 more players

Riley O'Brien

Or read one already written — Riley O'Brien against:

Similar players

Nearest 2026 seasons by command, run prevention and role, on rate statistics rather than totals.

Anthony NunezBAL

ERA: 4.07
FIP: 3.49
SO: 66
WAR: 0.8

Very close

Anthony BandaMIN

ERA: 4.46
FIP: 4.33
SO: 33
WAR: 0.1

Very close

Craig KimbrelTB

ERA: 4.50
FIP: 4.12
SO: 40
WAR: 0.3

Very close

Mason FluhartyTOR

ERA: 3.36
FIP: 3.67
SO: 65
WAR: 0.8

Very close

How these are computed

wOBA uses linear weights measured from this season's own play-by-play rather than published constants, and wRC+ is park-adjusted against that same league. dbWAR is our own open implementation — not fWAR or bWAR — and the full derivation, including its simplifications, is on the methodology page.