Sticky Free: K-BB Leaderboard Since Crackdown

·14 min read

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In this week’s “By The Numbers” breakdown the analysis will focus on pitching results since the foreign substance crackdown started on Monday, June 21. A previous edition of By The Numbers looked at possible arsenal changes that occurred due to the change in landscape, but now that we have a bit more data to play around with we can investigate a bit more.

It is important to remember the sample size we are dealing with, like always, as we are well within “hot streak” territory. This exercise is to pop the hood and check out who has been effective since the foreign substance checks were initiated, and who has fallen off a cliff.

Command and spin rates have been the primary variables that most have looked into so far, but in the end, those are not fantasy categories. Instead, we are going to dive directly into results and the all-important strikeout minus walk percentage. The idea is to identify starting pitchers who have been effective, and therefore possibly unaffected, but the foreign substance crackdown in order to locate value in the tail end of the fantasy baseball season.

Strikeout Minus Walk Percentage

There is a massive flaw in using K/9 or BB/9 to judge a pitcher since the result measures them on a per-inning basis. This is a mistake. The goal should be to have accurate statistics that measure how efficient a pitcher can be while still showcasing fundamental skills. This is where the K-BB percentage comes in.

Strikeouts are not the bedrock of successful pitching. Many pitchers get by generating weak contact and recording outs like Dallas Keuchel. However, strikeouts are a fantasy category and weak contact is not. Combine this with the fact that strikeouts measure both guaranteed “outs” and a pitcher’s ability to control and dominate opposing batters make it a useful measurement for success.

The issue is that you cannot be successful with strikeouts alone. A pitcher must have the ability to command those pitches or it will result in free admission on the basepaths. Walks are the worst and a high walk percentage has a high correlation with poor results. In this particular instance, the foreign substance crackdown has impacted many starting pitcher’s command more than their spin rate. No better way to (quickly) measure a pitcher’s command than digging into their walk rate.

To recap what we are looking for:

  • Strikeout Ability

  • Quality command (low walk rate)

It may seem obvious when you think about it, because it is. K-BB rate is the single most important metric for a starting pitcher in fantasy baseball and if nothing else you should take that lesson from this article.

K-BB Percentage Leaderboard

Below are the top-30 starting pitchers in K-BB percentage since June 21:

K-BB Top-30
K-BB Top-30

Aaron Nola, Phillies

The Phillies ace has been a disappointment to fantasy managers this season after being drafted near the first and second round turn in most drafts. The 28-year-old currently carries a 4.37 ERA and a 39.5 percent ground ball rate. Most of his issues may stem from a career-worst 1.40 HR/9 this season, but with a 29 percent strikeout rate and five percent walk rate there was bound to be a turnaround. After all, Nola did tie the major league record for most consecutive strikeouts in a game this season.

The right-hander is the major league leader in K-BB percentage since June 21 with a 33.3 percent mark. That is amazing seeing that the league average typically falls around 14 percent in years past. Nola currently boasts a 35.7 percent strikeouts rate during that span with a 2.4 percent walk rate. Unfortunately for fantasy managers, those metrics have come with a 4.80 ERA. The good news is that Nola also sports a 3.25 FIP, suggesting that better days are ahead for the Phillies ace.


The data suggests that a turnaround should be coming when you see a .231 batting average against and 1.03 WHIP, but should you expect results to follow?

Nola has clearly not been impacted by the foreign substance crackdown but is still having trouble with balls leaving the yard (1.80 HR/9 since June 21). The right-hander carries the 14th highest HR/FB ratio in baseball since June 21 and is getting barreled 9.2 percent of the time. Nola is going to have some gems in his back pocket down the stretch in fantasy, but the blowups are likely here to stay in 2021.

Nathan Eovaldi, Red Sox

If you have been paying attention, Nate Eovaldi being on this list should not surprise you. The veteran right-hander has been one of the most consistent pitchers in the entire league this season. Eovaldi’s performance has been consistent across the boards in almost every metric, which you can see in that chart below:

Eovaldi 15
Eovaldi 15

The 31-year-old carried a 3.49 ERA and 2.47 FIP on the season with a 2.45 ERA and 2.21 FIP since June 21. Eovaldi has posted a 27.7 percent punchout rate while giving out free passes just 1.5 percent of the time during that span.

Some may point to a .322 BABIP as a reason to expect even further production, but the right-hander has spent most of his career in that range so this was to be expected. Don’t be greedy.

Part of the reason behind Eovaldi’s success has been the reemergence of his slider this season. After abandoning the pitch after the 2018 season, despite carrying a 30.4 percent whiff rate, the right-hander brought it back this season better than ever. The slider and its 38.4 percent whiff rate have given Boston’s ace a true weapon for opposing hitters to chase while making his other weapons more dangerous.

Eo Slider
Eo Slider

The best part of Eovaldi’s improved plan of attack has been his ability to keep the ball in the yard. Home run suppression was a strength of the righty early in his career but has been swollen in recent years ranging from 1.49 HR/9 in 2020 to 2.13 HR/9 in 2019. This season that number has dropped to 0.39 and the change has been completely legitimate. A cutter that rides in on right-handed hitters and breaking pitches that dive out of the zone is a great way to limit hard contact.

The largest worry with Nathan Eovaldi has always been his health and this has soured his fantasy value in many player’s minds. Do not let it impact yours. The Red Sox right-hander has a solid game plan that has translated well past the foreign substance crackdown and is surprisingly one of the most consistent pitchers in the game right now.

Yu Darvish, Padres

If Nathan Eovaldi has improved due to home run suppression, Yu Darvish is the opposite of that. The Padres gyro-machine sits near the top of the leaderboard in K-BB since June 21 with a 27.8 strikeout rate and 4.5 percent walk rate, but with a 5.12 ERA and 4.35 FIP. What’s up with that?

A 1.99 HR/9 is what is up.

A 3.62 xFIP gives you an idea of how much the long ball has impacted Yu Darvish of late. This is especially worrisome since the right-hander HR/9 registered at an even 1.00 before the crackdown date.

Darvish Spin
Darvish Spin

Using the rfCommand metric from, Darvish grades out with a negative 2.4, with the league average being zero. This measures how much better (or worse) a given pitcher’s location is based on expected outcomes. As you can see in the charts below, the 34-year-old has been missing right in the heart of the plate.

Yu Zone
Yu Zone

Darvish certainly has the “stuff” to survive this typically, but if there has been a loss in his overall effectiveness, the heart of the plate is a bad idea. The Padres ace still carries one of the top K-BB percentages in the game since June 21, so this is not a signal for panic. A reminder that this could easily be a slump, those happen all the time. However, the warning signs are there. Darvish is pitching well until he misses. The problem is that his misses are killing him. Is this due to a lack of feel for the ball due to a loss of grip? Perhaps.

Gerrit Cole, Yankees

Gerrit Cole is bound to come up in any conversation surround foreign substances. The Yankees ace has become the unwilling poster boy for the subject. After the right-hander surrendered an eyebrow-raising six runs over five innings to the Red Sox on June 27, including three titanic home runs, there was understandable skepticism. When Cole followed that performance by allowing nine baserunners over 3 1/3 innings to the Mets on July 4, panic set in for most.

cole spin
cole spin

What happened next surprised everyone. The 30-year-old went out and tossed a 12-strikeout complete game shutout versus the Astros. The contest may go down as a defining game in Cole’s career after he demanded to be kept in the game, throwing 129 pitches in total. In the two games that followed the righty compiled 19 punchouts over 11 innings having allowed four runs, with just one home run allowed.

cole k
cole k

Cole is not dominating in the fashion he was before June 21, when he carried an American League best 31.2 percent K-BB rate, but he has made adjustments to stay effective. Will he be able to capture his previous level of success? That remains to be seen, but he seems to have put the worst behind him in terms of home run prevention. The issue to keep an eye on is command, with Cole having tripled his walk rate. If that trend remains consistent and the home runs pop back up you are looking at a problem.

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Lance McCullers, Astros

If you were to look at Lance McCullers numbers compared to the rest of the group, you might assume that there is a command issue. It would make sense considering that the right-hander is tied with Gerrit Cole for the highest walk rate on the leaderboard at 9.3 percent.

You would be wrong. Kind of.

There is certainly an issue with walks, but it has nothing to do with a foreign substance. McCullers actually carried a 12.9 percent walk rate before June 21 with a 12.9 percent K-BB rate. That’s right, the 27-year-old has not only avoided a downslide but has improved a 22.4 K-BB while striking out 31.8 percent of batters.

lance bb
lance bb

McCullers has posted a .297 expected slugging percentage against, which is in the top nine percent of the league while maintaining a consistent spin rate on his arsenal. The Astros righty is very dangerous when it comes to deception as his sinker mirrors both his curveball and newly acquired slider. The offerings look similar coming out of McCullers' hand before diverting in several different directions.

lance spin based
lance spin based

Health remains the primary concern for Lance McCullers, and if he has that you should fully trust him in fantasy.

K-BB Percentage Anti-Leaderboard

Now let’s take a look at the bottom-15 starting pitchers in K-BB since June 21.

k-bb bad
k-bb bad

Zach Davies, Cubs

You may see Davies' name and wonder why I would feel the need to break him down. The reason is simple. Zach Davies has a strong reputation over the last five years for not allowing free passes on the basepath, yet he sits with a walk rate of 14 percent.

davies bb
davies bb

The first thought may be to assume this is an isolated problem to the cherry-picked time period. It turns out that Davies has been struggling all season with bases on balls, with a walk rate of 11.1 percent before June 21. So why did his walk rate plummet while his results have improved?


Davies has enjoyed an 83.3 left on-base percentage while posting the lowest HR/FB ratio of his career (8.8 percent). The 28-year-old may have a 3.38 ERA since June 21, but with a 5.4 percent K-BB and the metrics above it’s a miracle that he has been able to avoid an implosion. There are no spin rate shenanigans going on here, but Davies is a certain fade in fantasy.

Framber Valdez, Astros

The Astros right-hander got off to a fairly late start thanks to an early injury in spring training but faired well during his first several starts. Framber allowed no more than one earned run over his first five starts from May 28 to June 13 and tossed seven innings of two-run ball on June 19 versus the White Sox.

In the six starts since Valdez has 16 earned runs over 34 1/3 innings and carried a 4.13 ERA so far in July (2.10 in June). So what happened? The 27-year old’s strikeouts rate remained consistent, but his walk rate jumped from 6.9 percent to 13.6 percent, which decreased his K-BB rate by 8.8 points.

framber bb
framber bb

Walks have been an issue for Valdez in the past, so this could simply be a recurring issue. However, given the timing of the downturn, it is worth considering whether or not we can expect a turnaround or if the loss of command is tangible.

Wily Peralta, Tigers

There is nothing much to discuss with Peralta, but given his recent success combined with his name showing up on the leaderboard, we might as well take a look.

The 32-year-old has posted an impressive 1.67 ERA since June 21 with a 0.90 WHIP. How can there possibly be bad news? There are many, many reasons, unfortunately.

  1. 0.90 WHIP with a nine percent walk rate

  2. .172 BABIP

  3. 89.21 percent left on base rate

Is there good news? Sure. Peralta has generated a 57.3 percent ground ball rate during this time frame with a 15.7 percent line-drive rate and 5.6 percent barrel rate. The results are not entirely false, but they are completely misleading. The Tigers’ right-hander has been a gift in fantasy for those that have been able to take advantage, but his 4.24 FIP and 4.74 SIERRA are a more accurate measurement of what to expect going forward.

Kyle Gibson, Rangers

It always seemed like Gibson was playing with house money this season. The Texas right-hander has posted amazing results and earned himself a trip to the All-Star game in Denver after posting a 2.17 ERA and 1.06 WHIP before June 21. The introduction of a cut fastball gave Gibson an extra weapon that allowed his slider to be more effective.

Gibson did seem to be living on the edge with an 11.8 K-BB rate, but it has now dropped to 9.2 percent thanks to a rise in free passes that has resulted in a 4.58 ERA since the target date. Natural regression could be argued as his .244 BABIP morphed into a .319, but a loss of command was hard to overcome.

It is unlikely that Kyle Gibson is going to regain his first-half magic unless he can harness his arsenal, especially his four-seam fastball.

gibson bb
gibson bb

Joe Musgrove, Padres

If you happen to be a fantasy manager with shares of Joe Musgrove you have witnessed what I am about to explain. The Padres right-hander has posted almost two entirely different seasons this year before and after the crackdown date.

  • Pre-June 21: 2.28 ERA, 0.85 WHIP, 31.5% K rate, 5.5% BB rate, 26% K-BB

  • Post-June 21: 5.34 ERA, 1.42 WHIP, 18.1% K rate, 8.0% BB rate, 10.1% K-BB

Musgrove has seen his batting average against rise from .137 to .306 this season while suffering a dramatic loss in whiff rate. So what is the issue?

joe spoin
joe spoin

As you can see, the issue is certainly not spin rate, as Musgrove has actually added RPM as the season has moved forward. Loss of command seems to be an overarching theme for struggling pitchers, which is to be expected in both this study and through general slumps.

The question is, is this a slump, regression, or an issue? Joe Musgrove was likely pitching above his head early in the season but is now pitching slightly below it. The data would suggest that the Padres righty is going to continue to struggle based on his track record and the timing of his slump in regards to June 21. Remember, most pitchers impacted by the crackdown were simply using a substance to gain grip, not bamboozle the hitters. Either way, Musgrove will remain a risk for the rest of the season in fantasy, but if Gerrit Cole has taught us anything, adjustments can be made quickly and implemented overnight. Keep an eye on Musgrove and be careful with starting him in tough matchups.