Pitcher Advanced Metrics Studs and Duds - K-BB% For Week 8

Welcome back to RotoBaller’s Statcast pitcher Studs and Duds article series! Each week, I will select one advanced metric, choose two pitchers with strong values and two with poor values, and analyze what those values may mean for future performance. This week, I will take a look at a metric that is not as complex as SIERA but still generally speaks to metrics within a pitcher's control: K-BB%.

The calculation for K-BB% is exactly as it sounds; a pitcher's walk rate is subtracted from their strikeout rate. Again, a pitcher is more-or-less in control of these two metrics, so they can help point to how strong overall a pitcher is. In general, a high K-BB% indicates that a pitcher is striking out hitters frequently without walking too many. Strikeouts, walks, and WHIP are important facets of fantasy baseball, so K-BB% can be used to indicate a pitcher's fantasy value.

K-BB% is a more accessible metric than SIERA and provides valuable fantasy insight. At this point in the season, players are starting to settle into their underlying metrics, meaning we are starting to get some larger sample sizes, which can be used to draw fantasy conclusions. With that in mind, let's take a look at a few K-BB% Studs and Duds!

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K-BB% Studs for Fantasy Baseball

All stats are current as of Sunday morning, May 29, 2022.

Nestor Cortes, New York Yankees
4-1, 1.70 ERA, 30.2% K%, 5.9% BB%, 24.3% K-BB% 

"Nasty Nestor"  Cortes was an intriguing SP/RP fantasy option in 2021 and has launched himself onto fantasy radars this season. The quirky pitcher has served solely as a starter for the Yankees this season and has an immaculate 1.70 ERA, 0.85 WHIP, and a 24.3% K-BB% that is just above teammate Gerrit Cole. Cortes has been a surprise fantasy stud so far this season, but can he keep this up?

The main component of Cortes' high K-BB% rate is his 30.2% strikeout rate. This is an elite rate, especially for someone who does not have overpowering stuff. Cortes relies mainly on an 86.1-MPH cutter and 90.8-MPH four-seam fastball. Consequently, he has a low 9.7% swinging-strike rate. However, his 18.6% called-strike rate is in the top-10 among qualified pitchers. Cortes is known for mixing up his deliveries and arm angles, which may help his called-strike rate, but this metric is more difficult to tie directly to a pitcher's skill than swinging-strike rate. As such, I would be very surprised to see Cortes maintain such a high K-BB% over the course of the season.

Cortes presents an interesting case for fantasy managers. On the one hand, he is clearly over-performing his K-BB% rate, as it is unrealistic that he can maintain such a high K% with his mediocre stuff. On the other hand, he has pitched well and has a 2.89 SIERA with an above-average batted-ball profile to back it up. I consider Cortes to be a sell-high candidate if other fantasy managers are willing to buy into him, but he should still be a relatively productive fantasy option in the event that fantasy managers aren't willing to do so.

Frankie Montas, Oakland Athletics
2-4, 3.12 ERA, 28.9% K%, 6.6% BB%, 22.4% K-BB% 

Despite playing for an uninspiring team, Frankie Montas has been a useful fantasy pitcher throughout his career. He had a strong 2021 season and is picking up right where he left off in 2022. The 29-year-old has a strong 3.12 ERA, 0.97 WHIP, and a 22.4% K-BB% over his first 10 starts and 57 2/3 innings pitched. Unlike Cortes, does Montas have the underlying numbers to fully back up his performance?

Fortunately, the underlying numbers and history support Montas' performance. He is slightly out-performing his relevant career averages; his K% is 28.9% compared to a 25% career mark, his BB% is 6.6% compared to a 7.9% career mark, and his swinging-strike rate is 14.1% compared to a 12.3% career mark. He has managed this while losing about one MPH on each of his pitches. However, the differences are not so great that I am worried about believing Montas' results. Further, his Statcast profile is strong overall, further supporting his current performance.

Montas won't be able to control the offense behind him, which will affect his win count. He can control other aspects of his game, and he has done a good job of that in terms of K-BB%. He has over-achieved slightly compared to his career numbers, but there is more than enough to generally support his strong performance. I think Montas will continue to be a valuable fantasy asset, even if he continues to pitch for the A's.

K-BB% Duds for Fantasy Baseball

All stats are current as of Sunday morning, May 29, 2022.

Ian Anderson, Atlanta Braves
3-3, 4.34 ERA, 17.6% K%, 11.3% BB%, 6.4% K-BB%

Ian Anderson is one of the many young, exciting pitchers in the Braves system. The 24-year-old has gotten off to a decent start to his career but has a mediocre 4.34 ERA, 1.34 WHIP, and a 6.4% K-BB% that is second-lowest in baseball through his first nine starts and 47 2/3 IP this season. Can he be a useful back-of-the-rotation fantasy option, or will his performance continue to decline in line with his K-BB%?

The first thing that stands out to me is Anderson's walk rate. His current 11.3% BB% is the highest in baseball among qualified pitchers and is not that much higher than his 10.3% career mark. Putting runners on for free adversely affects most pitching outcomes, but it directly makes it harder to have a good K-BB%. On the other side of the equation, his 17.6% K% is too low to make up for it and is poor in general. As I have mentioned in previous articles, pitchers can be successful without being huge strikeout pitchers, but they need to avoid damaging contact to do so. Anderson has not done that; his exit velocity and hard-hit rate are in baseball's 38th and 34th percentiles, respectively, to go with a 10.7-degree launch angle.

All in all, Anderson has not done much to instill confidence this season. His mediocre ERA and WHIP, high BB%, and low K% won't net him many fantasy points and won't offer much of an advantage in any roto categories. He still has appeal in dynasty leagues given his age, but I don't see him offering much fantasy value in redraft leagues if he continues to pitch as he has.

Madison Bumgarner, Arizona Diamondbacks
2-3, 3.35 ERA, 15.6% K%, 8.0% BB%, 7.5% K-BB%

Fantasy managers know that Madison Bumgarner has not been the pitcher he once was since sustaining various injuries, but his 2022 season has been a bit of a throwback. The veteran has a 3.35 ERA and 1.16 WHIP over his first 10 starts and 48 1/3 IP. However, his 7.5% K-BB% is the fourth-lowest among qualified pitchers. Fantasy managers may not want to fully buy back into MadBum, but is he worth keeping an eye on or streaming in favorable matchups?

Bumgarner is a savvy enough pitcher to change his pitching style based on what he has, but the bottom line is his stuff is no longer overpowering, leaving him a very slim margin for error. His K-BB% is so low because he only has a 15.6% K%, which stems from a pitch arsenal that has seen a dip in both velocity and spin rates. Bumgarner was never a huge strikeout pitcher but was able to generate an 11-12% swinging-strike rate in his prime, compared to a mere 7.7% mark so far in 2022. His Statcast profile paints a bleak picture as well, leaving little optimism that he will maintain his current ERA and WHIP.

Some pitchers are able to adapt as they age or recover from injuries, and Bumgarner has done that on the surface in 2022. Unfortunately, his numbers under the hood suggest that he has out-performed himself and it would not be surprising to see him regress to his 2020-21 numbers. His pitch arsenal is not nearly as effective as it once was, leading to a slight jump in BB% and a big drop in K%. This leaves very little room for error for Bumgarner and very little upside for fantasy managers.

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