In pitching, there’s a elementary rigidity between the 2 greatest outcomes you may get hold of: strikeouts and grounders. Strikeouts are clearly one of the best, however grounders are unimaginable too. Batters put up a .232 wOBA once they hit the ball on the bottom, as in comparison with .462 within the air (popups are one other class of fine batted ball, however I’m lumping them in with aerial contact immediately for simplicity’s sake). The factor is, the pitches that induce strikeouts have a tendency to not induce grounders, and vice versa. Sinkers don’t miss bats, and four-seamers don’t preserve the ball on the bottom. It’s fairly the bind.
There are, in fact, pitchers who can do each. Nolan McLean springs to thoughts. There’s peak Zack Britton, Framber Valdez at his curve-spinning greatest, some good Cristopher Sánchez video games maybe. For probably the most half, although, it’s actually onerous to do each. I got here up with a easy rule to measure how good pitchers have been at it final 12 months: divide grounders by two, add strikeouts, subtract walks, and divide by complete batters confronted. Aroldis Chapman, Jhoan Duran, and Andrew Kittredge paced the league in it final 12 months, with Shohei Ohtani and Mason Miller rounding out the highest 5. These guys have been all extremely efficient.
It’s early within the season, in fact, however are you aware who’s main baseball on this ratio in 2026? Nicely, it’s Mason Miller. Oops. I assume breaking baseball will try this. When you’re hanging out 70% of the blokes you face, in fact you’ll lead this measure. However the one different participant above 50%? That’d be Riley O’Brien, the brand new Cardinals nearer, who has been among the best tales in baseball up to now this 12 months.
When you’re not conversant in O’Brien’s work, that’s okay. Earlier than 2025, he wasn’t all that notable: 10.1 profession innings pitched, a 9.26 FIP, and greater than a stroll an inning. He was twice DFA’ed (by the Reds and Mariners); the Cardinals acquired him from Seattle for money. However in 2025, O’Brien turned a nook. He reduce his stroll fee to a manageable 11.1%, ran an unsustainably low .252 BABIP, and posted a 2.06 ERA (3.61 FIP) over 48 innings of labor. After St. Louis moved Ryan Helsley on the deadline, he even joined the workforce’s nearer committee, ending with six saves.
O’Brien is a good instance of the tradeoff between grounders and strikeouts. He’s sinker-dominant, sitting 97-99 with glorious motion. He mixes in two variations of a slider, a tough one and a sweeping one, relying on who he’s going through. For probably the most half, although, it’s sinkers for breakfast, lunch, and dinner. He’s thrown the pitch 60% of the time this 12 months, a profession excessive, and it’s working a juicy 75% groundball fee (his profession mark is 62%). If you wish to preserve the ball on the bottom, it is a nice technique to do it.
If you wish to strike guys out, this plan makes considerably much less sense. Sinkers don’t miss bats. O’Brien’s personal previous is a good instance of that. Even final 12 months, when he took an enormous step ahead, his strikeout fee was 22.6%, roughly league common. Once more, he was nonetheless lots good. You don’t need to strike the world out to be a great reliever, as long as you don’t let opponents hit dwelling runs. Grounders are nice!
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I’ve talked about that O’Brien is throwing extra sinkers this 12 months. Now let’s simply take a fast peek at his strikeout fee to see how a lot it plummeted, and… Wait, what?
Riley O’Brien’s Steady Enchancment
| 12 months | Ok% | BB% | GB% | SwStr% | Whiff% |
|---|---|---|---|---|---|
| 2024 | 23.9% | 17.4% | 38.5% | 9.8% | 24.7% |
| 2025 | 22.6% | 11.1% | 54.1% | 10.9% | 24.4% |
| 2026 | 33.3% | 0.0% | 69.0% | 13.5% | 28.9% |
Yeah, O’Brien goes full Britton in the mean time. He has a career-high groundball fee. He has a career-high strikeout fee and a career-low stroll fee. It’s solely been 13 video games, however it’s been an exceptional 13 video games. He’s by no means had a stretch this good in any of these three classes, not to mention all three without delay.
How’s he doing it? Before everything, he’s throwing a hellacious sinker, one which’s meaningfully higher than it was a number of years in the past. Check out the pitch metrics beneath, in addition to our two fashions’ opinions of the providing. He’s modified the form in a means I personally suppose is sweet, and he’s additionally discovered to find it much better:
Riley O’Brien, Chosen Sinker Metrics
| 12 months | Velo | H-Break (in) | V-Break (in) | PB Stuff | PB Command | PB General | S+ Stuff | S+ Command | S+ General |
|---|---|---|---|---|---|---|---|---|---|
| 2024 | 96.8 | -10.1 | 4.7 | 64 | 34 | 46 | 120 | 75 | 96 |
| 2025 | 98 | -9.5 | 3.7 | 61 | 45 | 50 | 104 | 98 | 104 |
| 2026 | 98.1 | -10.4 | 3.1 | 64 | 56 | 60 | 112 | 119 | 132 |
The fashions have at all times preferred O’Brien’s sinker form, however they’re each much more eager about his areas in 2026 than they have been previously. Generally, it’s powerful to determine what pitching fashions see with regards to location. However in O’Brien’s case, it positively isn’t. Right here’s the place he positioned his sinker in 0-0 counts in 2024 and 2025:
That’s a 52 command grade, mainly common. On the primary pitch of an at-bat, hitting the zone is vital. Right here’s the place he’s throwing his sinker to begin batters out in 2026:
Ah. That’s a 71 command grade, with no actual blemishes; few wasted pitches, few meatballs. In the meantime, when he received to 2 strikes, he let hitters off the hook too typically, whether or not by grooving one or lacking badly:
When you’re holding rating at dwelling, PitchingBot beloved the uncooked bodily form of those two-strike sinkers, hated the situation, and thus gave them a median grade total. Now check out his two-strike areas in 2026:
The stuff is actually the identical, however these areas are comically higher than the outdated ones. Only a few dangerous misses within the heart to go along with fewer wasted pitches? It sounds too good to be true. Given how few dots there are in these plots, it’s straightforward to know how fleeting this will likely but show to be. However for now? It’s fairly darn nice.
Now, among the worth of those nice areas comes from ending the at-bat proper there. O’Brien has thrown 29 two-strike sinkers and gotten 9 strikeouts, which is an 86th-percentile putaway fee. However extra importantly, he’s transitioned away from doing one of many worst issues you are able to do as a pitcher: give your opponent one thing to hit once they’re behind within the rely.
In 2025, batters hit .350 with an xBA of .363 once they made contact with one among O’Brien’s two-strike sinkers. That’s a whole catastrophe, to place it mildly. I get pleasure from this Baseball Savant view of it. Right here’s the place opponents tagged his two-strike sinkers in 2025:
Right here’s the place they’re placing them in play in 2026:
You don’t need to be an information scientist to see that the second image is best than the primary. Nothing heart reduce, nothing elevated; the common launch angle on these balls is a goofy -11 levels. It’s small pattern season, little question, however that’s nonetheless distinctive.
Usually, this is able to be the half within the article the place I present you ways O’Brien’s different pitches have complemented this enchancment in sinker command. There’s only one drawback: That hasn’t occurred. He’s doing a worse job finding his slider and sweeper than in prior years. Our fashions concur that they’re each down a hair in stuff. He’s changing fewer two-strike breaking balls into outs than he did in 2025. You may’t take a look at his secondaries and discover any hint of enchancment. They have been already strong, and so they stay strong, nothing extra. The sinker is the place the change has come.
This looks like it ought to be too good to be true. All O’Brien did is begin throwing his sinker to higher areas? However truthfully, mainly sure. Because it seems, command is monumentally vital with regards to outcomes. Stuff is steady. When you can spin the ball, if you happen to can throw it onerous, in case your arm slot creates deception, these issues stay true just about each time you throw the ball. Command isn’t like that. It’s massively variable. The perfect pitchers in baseball throw horribly positioned pitches. The worst pitchers in baseball dot the nook on the good time each from time to time. This makes me a bit anxious about O’Brien’s efficiency, in that his enchancment comes completely from a class that’s a lot much less steady than many of the issues I take advantage of to foretell efficiency. However alternatively, there are good causes to imagine that O’Brien’s command is a real change in expertise stage.
O’Brien didn’t begin throwing a sinker till becoming a member of the Mariners in 2022. He transitioned to the bullpen on the similar time, rising his velocity by round 4 mph within the course of, and he continued to throw tougher as he acclimated to life as a reliever. Regardless that he’s 31, most of his time in skilled baseball scarcely ready him for his present type. He was a soft-tossing starter who blended a four-seam fastball, a curveball, and a changeup. Now he throws three utterly completely different pitches, and his present slider strikes quicker than his outdated heater. His stroll fee spiked when he began throwing a sinker, as a result of he merely couldn’t command it. It’s cheap to anticipate some sort of studying curve with regards to location. He’s gotten higher yearly, and even when he backslides from his present elite type within the second half of 2026, there’s no cause to anticipate him to fall all the best way off. In any case, bettering constantly for years is an efficient signal that continuous enchancment will proceed.
I clearly don’t suppose that O’Brien is nearly as good as his 2026 statline – he has a 0.00 ERA. However I do suppose that he’s an amazing instance of the outdated adage that many relievers could possibly be dominant if they might determine the place the ball goes. I imply, come on. This man touches 101 with a demonic fastball, one which averages 3.5 extra inches of drop than the common high-velo sinker. His slider, the one I described as unchanged from final 12 months? It’s a 92-mph slider! His sweeper breaks 17 inches. If you get proper right down to it, O’Brien’s uncooked stuff seems to be like a pure slot in a closing function. That’s true of many relievers lately. However for lots of these guys, the satan is within the skill to find that nasty stuff. O’Brien was a transparent instance of this previously. Now he’s an instance of how shortly somebody can go from intriguing to plain.