Carlos Rodón's two-pitch dominance mirrors Jacob deGrom's. Their contracts might reframe starting pitching.

The phrase "95 and a slider" has long been scout-speak for a pitcher who has the building blocks to become a major-league reliever. But as fastball velocity lurched up and up and up in MLB, the phrase became less and less complimentary. Where it used to be a ticket to a steady, prominent bullpen role, as Baseball Prospectus wrote last year, the label is now "simply generic — a qualifier to reach the majors and perhaps reach it half a dozen times in a season, not an indication of a career there."

As part of that shift, a different meaning has emerged. The descriptor that traditionally referred to the two-pronged arsenal of a reliever could now apply to one baseball that just came out of Jacob deGrom’s hand.

But in muddling the meaning of "95 and a slider," deGrom — who recently bolted the New York Mets for the Texas Rangers in free agency — has become the apotheosis of the form, his groundbreaking dominance a crossover moment for aces who pitch like closers. Peak deGrom has whittled his pitch mix into something that strikingly resembles that of a shutdown reliever, even though he works as a starter: Just 100 mph fastballs and hard sliders, in combination. Rinse, repeat, strike out the side. The past two years, rendered about one season's worth of pitching by injury, deGrom has thrown his fastball or slider 89% of the time. And he has been just about impossible to hit.

Now, deGrom is not the first to do that or even the most extreme example, but he’s the one who broke contain. These days, more starters are narrowing their focus to their bread and butter, often a fastball and a slider that veers out of its shadow. It looks almost certain that this offseason’s two most lucrative pitching deals will go to arms throwing this way: deGrom and Carlos Rodón. The left-handed Rodón, a 30-year-old former top pick whose early career was besieged by injury, broke out after reconstructing his delivery in 2021. In a prove-it year with the San Francisco Giants last season, he doubled down on his fastball-slider combo, delivering one of those two pitches on an eye-popping 92.3% of his offerings.

And, well, it worked. Rodón put up a 2.88 ERA across 31 starts, and reports indicate that the bidding for his services might reach $200 million.

This is becoming the multifaceted, multimillion-dollar question for teams: How far can aces such as deGrom and Rodón push the closer mentality into the realm of starters? Does it affect their durability? And if this really works, how many other pitchers should try it?

The proliferation of the two-pitch starter

It's important to remember why bullpens are chock-full of guys throwing high fastballs, bendy sliders and nothing else: It's effective. It was effective when guys such as Jeff Nelson were doing it almost 30 years ago, and when Craig Kimbrel was doing it for the past decade, and it is currently wildly effective for Edwin Diaz, whose innings in games deGrom started often felt like a weird type of deja vu.

There are many distinctions between starters and relievers, many reasons pitchers get funneled into one discipline or the other. Do they have the control and command to work multiple innings without racking up a sky-high pitch count? How clean is their delivery? Can it be repeated consistently 90-100 times in a day? Do hitters figure them out when the lineup turns over?

For good reason, the depth of a pitcher’s arsenal has traditionally been a major factor in answering that last question. Seeing a major-league hitter two or three times in a game, for most hurlers, means finding at least a couple of ways to get him out.

Then there are the deGrom types challenging that notion. In 2022, 10 pitchers who threw at least 120 innings went fastball-slider for at least 80% of their pitches. That list includes AL Cy Young runner-up Dylan Cease, World Series hero Cristian Javier and Clayton Kershaw, who has just as strong a claim on pushing this envelope as deGrom.

Four of those pitchers took it even further, going fastball-slider a positively closer-ish 90% of the time or more and finding real results, as indicated by their park-adjusted ERA- marks.

Rodón, San Francisco Giants, 92.3% four-seam/slider, 73 ERA-

Brady Singer, Kansas City Royals, 92.3% sinker/slider, 81 ERA-

Hunter Greene, Cincinnati Reds, 94.7% four-seam/slider, 103 ERA-

Spencer Strider, Atlanta Braves, 95.2% four-seam/slider, 65 ERA-

(In ERA-, lower is better, and 100 is league average. A 90 ERA- indicates a pitcher was 10% better than that season’s average.)

The youth and upward trajectory of that group would signal that this is not a passing blip but an approach more teams might steer into. Strider — the muscle-packed, mustachioed Rookie of the Year runner-up — started in the big leagues as a reliever and probably would’ve remained one in … virtually every other era of modern baseball history?

But in the past 10 full seasons — 2012 through 2022, but excluding 2020 — there have been 32 recorded seasons of 120-plus innings in which a pitcher used his fastball-slider combo at least 85% of the time. Twelve of those seasons have come in the past two years.

The most extreme such season came in 2015 via a career starter who managed a surprising, sterling 3.06 ERA while floating between the rotation and the bullpen. That pitcher? The same man who just signed deGrom: Rangers GM Chris Young.

Can deGrom and Rodón sustain this method of pitching?

The calculus for Young and the Rangers with deGrom — and for whoever wins the bidding war for Rodón — is how to maximize their extreme levels of pitch weaponry and minimize their extreme levels of health risk.

The mixing and melding of MLB pitching roles is nothing new. Plenty of teams have tried starting young pitchers in the bullpen and then moving them to the rotation. Others have sharpened a pitcher's stuff in relief, then flipped him back to starting. The Tampa Bay Rays famously employed the opener tactic. All that to say: The lines around pitching jobs and how to do them are growing faint or disappearing entirely.

But the physical act of what we would’ve called “throwing like a reliever” a few years ago? There has been no sea change there. It's still extremely strenuous, but pitchers are finding ways to do it for longer periods of time. When Young, the very tall pitcher-turned-Rangers GM, was employing his fastball-slider-only repertoire, he was 36 years old with a fastball sitting 87 mph. He never averaged more than 91 mph on his heater in the majors. Rodón reached the majors throwing 94 mph, pretty hard for a lefty starter, and now sits 95-96 with his four-seamer.

It’s not just a divergence from conventional wisdom empowering the two-pitch aces. It’s the effort, the stuff. It’s the advancement of technology and research that have allowed pitchers to dig deeper and throw harder. Rodón (and deGrom and Strider, etc.) can work with two pitches because the pitches look like this.

Or at least, they can work with two pitches when they’re on the mound. But staying there has not come as reliably as the outs and swinging strikes. We know deGrom’s story: His fastball velocity skyrocketed from 96 mph to 99 mph between 2018 and 2020. But after three consecutive 200-inning seasons from 2017 to 2019, he has thrown a total of 224⅓ innings since.

Rodón was plagued by injuries while with the White Sox, missing huge chunks of every season between 2017 and 2020. So far, the retooled delivery that amplified his stuff has also kept him relatively healthy. But even in two mostly awesome years, there's a worrisome moment. His velocity fell off a cliff in September 2021, dropping to 93 mph from 96 the previous month and likely postponing teams' willingness to offer him his impending payday.

Virtually every starter is throwing fewer innings per season than they used to — because, repeat after me, they’re all putting more effort into each pitch — but this particular type of pitcher is on a more extreme curve. If you take every pitcher who threw at least 120 innings (some semblance of a full season), the average starter threw 179 innings in 2012 and 159⅓ in 2022. The 10 fastball-slider guys mentioned earlier averaged 145 innings. And deGrom didn’t make the minimum to be included there.

You can argue it’s still well worth the risk if pitchers like deGrom and Rodón continue to strike out the world and shut down offenses. But it’s an open question how long these pitchers, entering or well into their 30s, can sustain the current strategy. Worth noting: deGrom and Rodón aren’t actually two-pitch pitchers. Each of them has third and fourth offerings that they have used in the majors to great effect.

In 2016, Rodón's mix looked more like the diversified model some teams clearly prefer: Two different types of fastballs, the slider and a changeup making its way in at least 10% of the time. The Phillies, for instance, traffic in starters who use multiple shapes of fastballs, a breaker and an offspeed pitch; Aaron Nola, Zack Wheeler and free-agent addition Taijuan Walker all fit that bill.

Rodón cut his (often quite successful) changeup from regular usage in 2022, once he joined the Giants. People around the Mets love to talk about how deGrom actually has one of the best curveballs in baseball, too. In 2022, he injected it into the arsenal far more often … which means he threw it 48 times in 64⅓ innings. At least one of those times appeared to be purely to get a rise out of Max Scherzer, a scholar of the wide repertoire school of pitching.

For pitchers, changing teams often means changing mindsets. At the very least, it means changing coaches. The clubs vying to sign Rodón probably have an inclination of how they want him to pitch going forward and how they might control variables such as days of rest to aid his health. Those things could certainly factor into his decision. He reportedly chose the Giants last winter in part because White Sox pitching coach Ethan Katz endorsed the organization’s coaching philosophies.

Another consideration on the horizon: The pitch clock coming to MLB in 2023. Relievers often take longer between pitches to regain energy, and even though these particular pitchers don't have such extreme tendencies, not being able to take as much time to recharge might affect their outlook or health.

Where deGrom and Rodón go from here will be interesting to watch — for the teams' success, for their careers — and could prove influential to the mostly young pitchers following in their footsteps. Along with Strider, rookie Cincinnati Reds starter Hunter Greene, a former top pick, found his footing by riding with his fastball-slider combo. Cease and the White Sox are banking on it, and the Astros' Javier sparked a World Series no-hitter with it.

The outcomes here could turn back the clock and reconstruct the traditional starter mold. Or they could light the way to something very, very different: a game in which everyone throws 97 with a filthy slider, just a few innings at a time.