Baseball’s New Most Dominant Pitch

Baseball, without question, is going to be a worse game without Mariano Rivera. It wasn’t just that Rivera was consistently excellent. It’s that he was also unwaveringly humble and gracious, being the rare sort of Yankee you could like even if you rooted for a team of non-Yankees. But Rivera’s retirement does, at least, open up some questions that previously wouldn’t have been up for debate. When it comes to picking the best at something, Rivera’s absence gives a chance to somebody else.

I was asked in my Tuesday chat to identify the new most dominant pitch in baseball. Before, the answer was automatic: Mariano Rivera’s cutter. It was that way for nearly two decades, as Rivera rode one masterful pitch to glory and a certain place in the Hall of Fame. Rivera never really declined, and his cutter topped the list because of his command, his results and his longevity. But now we’re able to entertain the idea of other pitchers and other pitches. With Rivera out of the picture, choosing another pitch isn’t blasphemous. The way I see it, there are two contenders.

Rivera debuted in 1995, but he wasn’t himself yet. He was still thought of as a potential starting pitcher, and he didn’t find his groove until the next season. From that point forward, Rivera allowed a 42 OPS+. Recall that a 100 OPS+ is average, and a 99 OPS+ is above-average, for a pitcher. The difference between an average OPS+ allowed and Rivera’s OPS+ allowed is Sergio Romo’s OPS+ allowed. Rivera was pretty good.

Craig Kimbrel, so far, has allowed a 28 OPS+. He’s been completely absurd. It would be hard to argue against the idea that Kimbrel has been baseball’s most dominant pitcher. But is he in possession of baseball’s most dominant pitch? I don’t think so, because he throws two dominant pitches with his fastball and his curveball. It makes it hard to separate one from the other. It’s interesting what happens if you follow along on the list.

Remember that Rivera, as a full-time reliever, allowed a 42 OPS+. So far, Aroldis Chapman has allowed a 42 OPS+. And, so far, Kenley Jansen has allowed a 43 OPS+. Also significant, for our purposes here: Chapman has thrown a whole bunch of fastballs. Jansen has thrown a whole bunch of cutters. According to the PITCHf/x information we have, and courtesy of Brooks Baseball, later-career Rivera threw 89% cutters. Jansen has thrown 89% cutters. Chapman has thrown 85% heaters. While neither is exclusively a one-pitch pitcher, neither was Rivera. They’re just mostly one-pitch pitchers, like Rivera, and that’s why I’ve settled on this particular pair of candidates.

This is different from finding baseball’s most unhittable pitch. That’s simply ordering pitches by swings and misses. What made Rivera’s cutter so dominant was hitters couldn’t hit it even when they basically knew it was coming. That’s how it’s been with Jansen’s cutter, and Chapman’s fastball. Cole Hamels, for example, has thrown an outstanding changeup, but it would probably be a lot less outstanding if he threw it nine times out of every 10 pitches. Pitches rely on one another; every pitch is connected. Rivera’s cutter relied on itself. Jansen’s cutter relies on itself. Chapman’s fastball relies mostly on itself. I don’t know if there’s an objective way to calculate the game’s most dominant pitch, but for me, frequency scores major points.

Because of that, I actually slightly favor Jansen’s cutter. Chapman has thrown a slider 15% of the time, and it’s extremely different from his fastball. Jansen has thrown a slider 8% of the time, and last year it was below 6%. Jansen is more of a one-pitch pitcher than Chapman is, and so I give extra credit to his cutter. Still, I couldn’t in good conscience write this just about Jansen without acknowledging Chapman’s unhittability. Pick whichever pitch you want between them, and I won’t argue. I’m just picking Jansen’s.

The following is a table of information, from Brooks Baseball. This covers the PITCHf/x era, so it misses a lot of Rivera, but gets all of the other two guys. And, for Rivera, it should be fairly representative.

Pitcher	Pitch	Strike%	Contact%	BA	ISO
Rivera	Cutter	69%	79%	0.192	0.077
Jansen	Cutter	68%	66%	0.159	0.086
Chapman	Fastball	64%	66%	0.177	0.088

Rivera, of course, wasn’t a strikeout pitcher in the style of Jansen or Chapman. Rivera’s strikeout rate peaked at 31%; for his career, he struck out about a quarter of all batters he faced. Jansen has struck out two-fifths of the batters he’s faces, and Chapman’s exactly the same. Rivera was famously able to induce weaker contact, because of his movement and command. Jansen’s cutter and Chapman’s fastball have yet to be pounded, but they’re just different pitches in style and intent.

I don’t refer to pitch-type values very often, but I will note this: Rivera’s cutter was worth around two runs better than average per 100 throws. That is, over the part of his career for which we have appropriate records. Chapman comes in around +1.2 runs per 100 fastballs. Jansen’s at about +1.8 runs per 100 cutters. There’s a lot that goes into these numbers, and they’re too complex to be tremendously useful, but they can at least be indicative of things, and so consider this confirmation that Jansen has a great cutter and Chapman has a great fastball.

A little more before I let you go. Chapman is no longer the hot mess he was in 2011. The past two years, he’s increased his fastball strike rate. Jansen’s even more interesting, because he was a catcher as recently as 2009. He’s still relatively new to pitching, so he’s still making some improvements. Here’s his cutter strike rate by year:

2010: 64%
2011: 66%
2012: 68%
2013: 70%

The thing about Jansen is he’s aggressive with his cutter in the strike zone. He doesn’t have Rivera’s impeccable command, but his command is plenty good and the quality of his cutter gives him a greater margin of error. He’s able to get away with more. Last year, batters swung through 30% of Chapman fastballs right down the middle. They swung through 33% of Jansen cutters down the middle. More often than not, with Jansen, hitters are going to get a cutter somewhere in the zone. That knowledge hasn’t helped them yet.

You don’t need to see Chapman’s fastball. You know what an Aroldis Chapman fastball looks like. You might be more curious to see Kenley Jansen’s cutter in action. So, as .gif relief, he’s Jansen carving through Yadier Molina last October:

Perfect, all of them. Kenley Jansen isn’t perfect, but neither was Mariano Rivera. He’s been about as close as humans can get, and he’s done it in large part with one pitch, a fastball with cut movement that just came to him naturally. Jansen and Rivera have a surprising amount in common, which should maybe be less surprising given that the former has extensively studied the latter.

With Mariano Rivera retired, which is the new most dominant pitch in baseball? Forced to choose, I’d say it’s Kenley Jansen’s cutter. Close behind, there’s Aroldis Chapman’s fastball. Craig Kimbrel is probably the most dominant pitcher in baseball, but that’s a different subject. Of course, we can’t think of Jansen’s cutter or Chapman’s fastball in the same way we think of Rivera’s cutter. One of the things that made Rivera’s cutter so extraordinary is he threw it so well for so many years. In that regard, Jansen and Chapman have a long way to go, with an awful lot to prove. But then, Rivera’s cutter was an all-time pitch, and you wouldn’t expect somebody to throw something just as good for just as long. Jansen’s cutter is amazing for now, and that’s good enough. Sadly, Rivera’s no longer an active pitcher in the peer pool.