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MLB Deserve-to-Win
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Riley O'Brien

2026
Cardinals· RHP · throws R· 64.0 IP· 4.08 ERA· 1.28 WHIP· 276 batters faced
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Grade

His grade shows how good he has been, and at what.
Fbetter than 22% of qualified pitchers at limiting bases
RelieverPower Arm

Misses bats in bunches; lives with the walks.

O'Brien allows more bases than most pitchers

The simulator expects him to allow 0.471 bases per batter faced, better than 22% of qualified pitchers. His best skill is limiting home runs (83rd percentile). His weakest skill is limiting hard contact (24th percentile). Short relief outings push strikeout rates up a little, so read his K% spoke with that in mind.

His grade rests on 276 batters faced, with data through 2026-09-27.

How to read this chart
Each spoke is a skill estimate adjusted for sample size, not a raw season stat, and farther out is better. A ↓ marks a stat where a lower number is better, and its spoke is flipped so farther out still means better. The middle ring marks the league median and the outer ring the league best. Percentiles compare him with 517 qualified pitchers, those with 100+ batters faced, starters and relievers together.

Plays like…

Each of these pitchers shares his archetype and sits closest to him in xEB/PA. Pick one to see him side by side with Riley O'Brien.

Nate PearsonRoyalsSam MollRedsJosh EknessMarlinsCole WilcoxMariners

Pitcher type

This map shows what kind of pitcher he is, next to the league.

Pitcher type

He lands in the “Hit hard, few strikeouts” corner of the map.

League best:K% − BB% Jacob Misiorowski (26.8%)Hard-hit% allowed Blake Snell (29.0%)

How to read this chart
Two skills separate pitching styles: strikeout rate minus walk rate, where higher is better, and hard-hit rate allowed, where lower is better. The hard-hit axis is flipped, so the best corner is the top right. Each dot is a pitcher with 80+ batters faced this season, sized by batters faced. The dashed lines are the league median on each skill, and the league best on each is named above the chart. Click any dot to open that pitcher's page.
 Riley O'BrienLeague medianPercentile
Bases per ball in play(lower = better).547.527—
Walk rate(lower = better)10%9%26th
Strikeout rate(higher = better)23%22%59th

A higher percentile is better, and the 99th is the top of the league.

Arsenal

These cards show what he throws and what each pitch does.

Riley O'Brien leans on his sinker (58% of pitches). His sweeper has performed closest to league average, with a 47% whiff rate against a league median of 31%.

Pitch mix & swing-and-miss

+21 bases better than a replacement arm this season

He allowed about 123 estimated bases, against a replacement arm's 144 over the same batters faced.

Replacement level is per-batter and can't be split by pitch type, so the bars below use league average.

All pitches

He cost 6.9 bases against league average across 1,052 pitches, or 0.7 per 100 pitches.

Sinker
58%
97.7 mph · RHP median 94.7
17% whiffs · Lg median 13%
cost 0.5 per 1003.2 total
Sweeper
33%
82.9 mph · RHP median 83.5
47% whiffs · Lg median 31%
saved 0.1 per 1000.4 total
Slider
8%
90.6 mph · RHP median 86.9
21% whiffs · Lg median 33%
cost 5.0 per 1004.1 total

He rarely throws his changeup (1% of his pitches).

How to read this chart
Each row is a pitch he throws at least 3% of the time, from pitch tracking in the regular season. The bar is how often he throws it, then its average velocity and its whiff rate, the share of swings that miss. Beside the velocity and the whiff rate is the median for that pitch, among pitchers of his hand for velocity and across the league for whiffs. More whiffs are better for a pitcher, while usage and velocity describe how he pitches. The Bases vs average bars score each pitch against a league-average pitch in the same count, and a bar to the left (saved) is better.

Mix by batter side

Sinker
56% vs LHH · RHP median 16%
61% vs RHH · RHP median 33%
Sweeper
31% vs LHH · RHP median 17%
35% vs RHH · RHP median 29%
How to read this chart
Each row shows how often he throws a pitch to left-handed hitters (LHH) and right-handed hitters (RHH), next to the median for pitchers of his hand (RHP median). Medians come from right-handed pitchers who throw that pitch at least 3% of the time. Between 131 and 213 of them qualify, depending on the pitch. A mix is a plan, so a higher or lower share is neither better nor worse. Overall results by batter side are under Platoon splits.

Riley O'Brien's pitch movement, 2026

His Sweeper and Slider have moved 2+ inches from their early-season shapes.

The verdict above compares each pitch with his own early-season outings in 2026, not with other pitchers, after taking out the league-wide drift in break.

Riley O'Brien's pitch movement, 2026-12012-12012in← glove sidearm side →more risemore drop
SinkerSI
Rise 4.8 in
−3.5 vs Lg median
Break 15.4 in
+0.2 vs Lg median
Vs. early season steady
SweeperST
Rise −4.7 in
−5.8 vs Lg median
Break −13.5 in
+0.3 vs Lg median
Vs. early season changed
SliderSL
Rise 0.6 in
−1.2 vs Lg median
Break −1.6 in
+2.1 vs Lg median
Vs. early season changed
Early season → nowLg medianNormal wobble around the dot
How to read this chart
Each dot is a pitch's current break in inches, averaged over his latest outings. Higher is more rise and further right is more arm-side break, and neither is better or worse. The faint trail runs from his early-season outings to the dot, and the soft halo shows how far normal noise can move it. League median is the small hollow ring, and a pitch marked * has none because too few pitchers throw it. The “changed” verdict removes a league-wide drift that the trail still shows, so a long trail can read as steady. The by-appearance chart below has the exact dates. More on the About page

By appearance

These charts follow his velocity, movement and mix from outing to outing.

These charts follow his velocity, movement and pitch mix one outing at a time, and each pitch keeps the same color in every chart. The velocity and movement charts also shade the middle of the league for scale.

Platoon splits

This section splits his results against lefties and righties.

Platoon splits (EB/PA allowed)

He handles righty bats better than lefty bats, by 0.042 EB/PA allowed.

50% probable range: +0.034 to +0.050

vs LHB150 PA0.454

vs LHB: shrunk estimate 0.454 EB/PA, 50% probable range 0.435 to 0.473, based on 150 plate appearances. Raw (unshrunk) rate: 0.508 EB/PA. League median vs LHB: 0.451 EB/PA.

His raw rate vs LHB (0.508) is off this scale. Small samples can push a raw rate this far, which is why the dot, the shrunk estimate, is the number to trust.

vs RHB127 PA0.412

vs RHB: shrunk estimate 0.412 EB/PA, 50% probable range 0.393 to 0.431, based on 127 plate appearances. Raw (unshrunk) rate: 0.448 EB/PA. League median vs RHB: 0.435 EB/PA.

0.3840.4080.4330.4580.482
← betterworse →
Below league medianAbove50% probable rangeHis raw rateMiddle half of the league

His split is about typical for a righty arm (median 0.042).

How to read this chart
  • Each dot is his estimate against that side, with its 50% probable range as the bar. These are bases allowed, so lower is better.
  • The diamond is his raw rate, which small samples make noisy, so the simulator pulls the dot toward a more trustworthy value.
  • The dashed tick is the league median, and the shaded strip is the middle half of pitchers with 100 or more batters faced.
  • The two splits average back to his modeled overall EB/PA allowed, not the xEB/PA headline.
  • Tap or hover a mark for its number. LHB and RHB are left- and right-handed batters. More on the About page

Contact allowed

These cards show what hitters do when they make contact.

Batters go up the middle off him most often, but they do the most damage to the pull side.

Pull side and opposite field depend on which side each batter hits from, so this pools every hitter he faced.

Batted balls allowed

Every ball hit off Riley O'Brien this season is drawn where it landed.
hit · out
EBlowhigh
vs Nick CastellanosHome run
105 mph · 25° · worth 3.8 bases
05/10 vs Padres
vs Jac CaglianoneHome run
108 mph · 34° · worth 3.7 bases
06/21 vs Royals
vs Pete Crow-ArmstrongDouble
110 mph · 21° · worth 3.1 bases
05/29 vs Cubs
vs Vaughn GrissomDouble
103 mph · 26° · worth 3.1 bases
07/20 vs Angels
vs Kyle SchwarberHome run
109 mph · 33° · worth 2.9 bases
08/23 vs Phillies

Luck check

One out behind him came on a ball the simulator values at 1.5 bases or more.

vs Dylan CrewsOutLucky out
103 mph · 22° · worth 2.1 bases
09/20 vs Nationals
How to read this chart
Dot color is estimated bases (EB), what the contact was worth no matter what the defense did with it. Darker means more bases, so a dark hollow ring in the outfield is a crushed ball his defense ran down. Tap or hover a dot or a row to link the two, and use the ▶ links to watch a play on Baseball Savant.

Deserved vs. actual

Batters have been credited with about 16 fewer bases than their contact off Riley O'Brien deserved, so his results have been lucky so far.

Deserved by the contact he allowed94
Actually credited to batters78

Both bars count 172 balls in play, with walks and strikeouts left out.

How to read this chart
Every ball in play is worth the bases its exit velocity, launch angle and direction usually produce. If batters were credited with more than that, his results have been unlucky, and fewer means lucky. BABIP against is the batting average on balls in play he allows, next to the league median.

ERA 4.08 · WHIP 1.28 · BABIP against 0.287 (Lg median 0.286)

Best games

These are his biggest outings this season.

Best games

These are his best outings this season, ranked by bases saved against a replacement arm.

Multi-season trends · Riley O'Brien

Compared with last season, his HR allowed% is up, his Barrel% against is up, his Hard-hit% against is up, his GB% against is down, his FB% against is up and his Pull% against is down.

Actual rates show what happened on the field, season by season.