Pitchers to File Away by K-BB%

The same stat is telling different stories about these pitchers.

If you came to hang out last week, you’ll know we talked about pitchers to file away by SIERA. The idea was that SIERA does a modest job in helping predict ERA for the next year. That kind of perspective helps because it means we don’t have to feel totally crazy buying into Framber Valdez or Zach Eflin, or about still feeling good over Chris Paddack. It can give us a nod on guys like Kevin Gausman or Frankie Montas.

K-BB% functions in a similar way. Though it doesn’t carry the same weight in correlating to the next season, it’s the best in-season indicator of how a pitcher is performing (and has possibly changed) which helps us figure out what to believe in. It’s also delightfully simple: how many hitters is a guy striking out, and how many walks is he giving up? It’s the core premise of pitching. Strike guys out, or, at worst, don’t let them get on base for free.

The league average K-BB% hovers around 14. For the purpose of this exercise, we’re examining some of the most curious names as determined by who has added or lost the most off their 2019 number. You can see the whole list of guys who have thrown at least 40 innings this year and 60 the year before here. Those parameters let us consider the weirdness of this season plus nearly any debut from 2019.

K-BB% Curiosities, 2020


Zach Davies 


Zach Davies might be the most interesting case of Padres’ magic this season. He’s having a career year while throwing softer than he ever has, and that’s saying something. His average sinker is coming in at 88.6 mph, which is nearly four full ticks slower than average. It’s never been about velo for Davies, though. 

As a guy whose fastball is slow, he’s left to work the edges and catch hitters off guard. The story shapes up when we see he’s collected the 16th-most called strikes in all of baseball this year, with his sinker getting one for nearly every three thrown. It really comes to life when we see he’s getting more called strikes in the shadow zone than any other pitcher in the majors. Any batter who steps into the box knows he’s going to see a bunch of stuff that’s questionable to swing at but also fairly likely to garner a strike. Woof. 

Everything Davies is throwing this year is also moving pretty much the same way it always has. His release points from year-to-year look like a rollercoaster but he makes it work. The only real difference is that his cutter and changeup have the closest release points of his career. He’s committed to the cutter more and more in the last two seasons and now he throws it 17% of the time, so having something that breaks the opposite direction of his sinker and changeup helps. The cutter itself is underwhelming — it garners below-average strikes and, accordingly, has allowed a wOBA higher than average — but the changeup seems to be benefiting. It’s easily his best pitch, which explains why he’s throwing it more than ever and just as much as his sinker. 

The book on Davies this year seems to be that he’s sprinkling in just enough of everything to make something especially tasty. In that sense, it’s easy to understand the bump in K-BB% but we might need to see this over a longer period of time before seriously buying into it. There’s just such little room for error when you’re throwing 88.


Zac Gallen


Gallen Gals, rejoice! Zac Gallen’s appearance here is another testament to just how steady he is. That might be the number one trait we should treasure in a pitcher. Think about it — how many guys can we really count on year-in, year-out? It’s an enormously valuable trait whether the guy is good, bad, or mediocre. You don’t have to worry about him putting up a “cherry bomb” or if he just threw his own “birthday party”. He is what he is, and so much of the heavy lifting we have to do when it comes to analysis is already done.

Specifically for Gallen, his Ks are down a little bit but his walks are just about in lockstep. The strikeout rate remains well above average while the free passes are down to almost exactly league average. The biggest changes in his arsenal regard some additional drop on his changeup and a curve that pushes less to the arm side. His biggest project this year seems to be his slider. Gallen has upped his usage of the pitch by nearly 7% but he’s getting a lot fewer whiffs with it. One reason why could be is he’s throwing it in the zone less. And by “it,” I mean everything. He’s only getting about 38% of pitches over the plate this year, compared to the league average of nearly 50%. It’s fair to wonder if he threw anything in the zone more if guys would be more willing to chase the slider.

That said, what Gallen is doing is also working, so any criticism is more picking nits about his game than poking holes in it. At just 25, he’s thoroughly exciting.


Max Scherzer


In the end notes of last week’s piece, I mentioned how it might be time to start regarding Scherzer’s back injury when considering how to evaluate him, despite his still-excellent K-BB rate. I knew then that it remained well above average at 23.8%, despite being down nearly 7%. The context I didn’t have until this piece is that’s one of the biggest drops among qualifiers. Only four other guys have lost more of an edge in 2020 — one of them is Gerrit Cole — but none of them are as old or have as much wear on their bodies. The greats can lose some zip and still be good; it’s one of the luxuries of having such elite talent. But writing off a bumpy 2020 for Scherzer and counting on him being the best version of himself next year might be ill-advised.

Check out this list of pitchers who threw into their age 36-37 seasons over the last 100 years — the age at which Scherzer will pitch next year. It has their K-BB% in those games, plus from their age 35-36 games and the difference between the two. Even the top-10 is illustrative.

K-BB%, 37-year-old Pitchers


For one thing, there are only two dudes above 20%. One of them saw a big drop between 36 and 37. The other was a freak of nature throwing from the left side. There’s one current noteworthy name missing because of injury this season: Justin Verlander, who presents another dubious case. Everyone else? The K-BB rate gets pretty pedestrian pretty fast. You could argue that, like Randy Johnson, Max Scherzer is a bit of a freak of nature. You could say hitters whiff more now than ever, so a drop for Scherzer might not be as drastic. You could even argue some World Series hangover was bound to happen, and that next year will be a clean slate. Any of those arguments is fine. That doesn’t mean they’re ones you’d want to hang your hat on when listing your no-brainer aces next year, though.


The Others


It’s impossible to mention Gerrit Cole immediately above and only glance over him as a footnote. It seems important to remember that 1) Cole had a historic season last year, so a step back was nearly guaranteed, and 2) there is something to players pressing when moving to new teams. He turned 30 only two weeks ago. It’s not time to worry about him yet. Patrick Corbin, whose K-BB% is down 4% in 2020, might be of concern moving forward because so much hinges on his unicorn slider. He’ll play next year at 31-32. Framber Valdez and Zach Eflin, mentioned at the top, both showed up as two of the biggest gainers in K-BB rate this year, which gives another reason to potentially buy into them for 2021. Aaron Civale is there, too, and I wrote about him a few weeks ago. Dylan Bundy and Kevin Gausman were right next to each other as gainers on this list — sorry, Orioles fans.


Photo by Russell Lansford/Icon Sportswire | Adapted by Justin Paradis (@freshmeatcomm on Twitter)

Tim Jackson

Tim Jackson is a writer and educator who loves pitching duels. Find him in the PL Discord, editing, managing, and podcasting with @BREAKINGPodPL here or writing at Baseball Prospectus.

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