RADIO
We’ve talked about how a pitcher’s SIERA is greatly influenced by their strikeout and walk rates, with the idea being that creating your own outs deserves more value while allowing batters to reach base for free is the devil. Perhaps you enjoy seeing more focused metrics, or would simply rather see the strikeouts and walks dimension alone.
Here’s where a pitcher’s K-BB% can help you. This percentage is derived from taking a pitcher’s strikeout rate per plate appearance and subtracting their walk rate per plate appearance. If a pitcher strikes out 20% of batters faced and walks 10%, then his K-BB rate will be 10%. All stats presented will be as of May 16.
Why You Should Care About K-BB%
Prescribing that one targets those who lead the league in strikeouts isn’t providing any groundbreaking insight, and the same goes for saying “avoid pitchers who walk a lot”. Perhaps you’ve heard of K/9 and BB/9, which is the amount of strikeouts and walks over nine innings. The idea being that every pitcher is graded on a per-inning basis that can be easily compared with one another. These rates have their place, but we can do better.
Using K% and BB% compared to those aforementioned metrics may not seem like much, but it does make a difference. Utilizing “per-inning” metrics invites extraneous wrinkles into the equation when we’re just concerned with strikeouts and walks. Analyzing strikeouts and walks per plate appearance gives the best look at the talent of the pitcher in correlation with how efficient they are. Let’s illustrate this with three scenarios:
Pitcher A strikes out the side in order, a 1-2-3 inning.
K/9: 27.00 (three strikeouts in one inning, multiplied by nine innings, gives 27).
K%: 100%.
K-BB%: 100%.
Pitcher B strikes out the first two batters, then allows consecutive singles before getting a strikeout to end the inning.
K/9: 27.00.
K%: 60%.
K-BB%: 60%.
Pitcher C also strikes out the first two batters and then allows consecutive singles, but then walks a batter before striking out the next guy to end the inning.
K/9: 27.00.
K%: 50%.
K-BB%: 33.3%.
As you can see, Pitcher A performed the best out of all three. Pitcher B did pretty well, but did allow two hits, making his appearance not as strong as Pitcher A’s. Pitcher C was the “worst” of the bunch, allowing half of the batters he faced to reach base. Let’s look at how each metric frames their performances though, and you’ll see why K-BB% deserves your attention.
K/9 says all three of those pitchers performed equally and would be tied on a leaderboard with a perfect 27.00 mark. The metric isn’t wrong, they all struck out three batters for their three outs, but you can plainly see that A > B > C should be visible.
K% does reflect the A > B > C hierarchy at least, with 100%, 60% and 50% rates, respectively. That means we’re on the right path, but that walk surrendered loaded the bases, extended the inning, and will force the pitcher out of the game earlier, so we'd like to account for it.
K-BB% shows the A > B > C gap, reading at 100 > 60 > 33.3. We now have a clean and concise figure that can speak to pitcher effectiveness and efficiency. Don’t get anchored by the lofty numbers, as the current league average for all starting pitchers’ K-BB% is 12.2% (it was 12.3% in both 2014 and 2015, so this seems rather steady for this era). Additionally, the average strikeout rate is 20.3% with an 8.2% walk rate in case you're exploring yourself.
Now that we’ve established the legitimacy of K-BB%, let’s get some actionable intel going.
2016 K-BB Leaderboard
- Clayton Kershaw – 32.4% (!)
- Drew Smyly – 25.4%
- Noah Syndergaard – 25.3%
- David Price – 24.8%
- Aaron Nola – 24.1%
- Max Scherzer – 23.9%
- Jose Fernandez – 23.5%
- Stephen Strasburg – 22.9%
- Vincent Velasquez – 21.1%
- Taijuan Walker – 20.5%
Most names aren’t surprising, but Smyly, Nola, Velasquez and Walker might raise some eyebrows. Smyly’s done well before, but his injury history has always pushed him down in rankings. Nola and Velasquez are both youngsters with promise, but many dismiss them due to pitching for Philadelphia. Walker was decent last season, but his 4.56 ERA raised questions.
Needless to say, these pitchers are riding healthy strikeouts along with fantastic control to success in 2016. Owning any one of these pitchers is a good thing and their performances should be respected. Let’s look at another dimension illustrated by the list, shall we?
Drew Pomeranz is 11th, just missing the cut, but he joins Fernandez, Danny Salazar and Rich Hill as the only ones in the top-25 with a walk rate over 10%. This means that they’re striking out a ridiculous amount of batters, enough to compensate for walks surrendered. This raises the “efficiency” point, as these guys still have value but are hard-pressed to regularly work deep into games. There’s a reason they only make for four out of 25 though, as it’s difficult to strike out as many as they do and the relative value of their strong strikeout totals is worth noting.
Using the K-BB% Diving Board to Launch Investigations
In conclusion, K-BB is a nice metric for those who enjoy analyzing a pitcher for outcomes that they can control (umpires play a part of course), but want something a little more tangible than SIERA’s complex formula. The idea here is that K-BB works beneath more fluke-influenced stats (like ERA) and speaks to a pitcher’s true talent. David Price has a 6.00 ERA despite being fourth in K-BB. Corey Kluber is 19th in K-BB but has a 4.30 ERA. They’re still good.
As always, no one statistic makes for an answer. Pitchers can still get lucky/unlucky on balls in play, allow an abnormal amount of homers, work with different pitch velocity, and so on. K-BB is a wonderful starting point for those seeking a focused metric regarding pitcher effectiveness and efficiency that correlates to true performance. Use these tools, investigate, ask questions, follow threads and win.
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