Biggest K-BB% Fallers - Starting Pitcher Fantasy Baseball Warning Signals for 2025

If you ask a dozen experts which statistic they believe is the biggest indicator of a pitcher's success, you will likely get close to a dozen different answers. However, I also think most of them would agree that a pitcher's strikeout-minus-walk rate (K-BB%) accurately reflects their overall performance.

In the complex world of baseball statistics, sometimes simpler is better. When it comes to K-BB%, the bigger the number (which represents a wider gap between their K% and BB%) the better. For reference, the average K-BB% last season for starters who threw at least 100 innings was 15%.

For this piece, I looked at all starting pitchers who threw at least 100 innings in the last two seasons to see which pitchers had the biggest decreases in their K-BB% from the 2023 season to the 2024 season. Let's see which pitchers saw the biggest decreases in this important ratio last year.

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Biggest Decreases in K-BB% Last Season

The pitchers appearing on this list are showing warning signals for fantasy baseball. Whether it's less strikeouts, more walks, or both -- the declines in K-BB% may be a sign of trouble for 2025:

From Good to Average K-BB% Fallers

The "There Are Reasons to Be Concerned" Pair

Kevin Gausman (-9.9% decline)

Gausman's gap closed up more than any other regular starter other than Griffin Canning - who had a terrible year. Gausman's year was not a total disaster but was a significant step back from what he had seen from him in San Francisco and Toronto for a solid four years in a row.

His strikeout rate dipped to just 21.4% after resting in the 28-32% range from 2020 to 2023. When you look at his pitch mix, he threw his usual stuff (four-seamer and split-finger) but saw the velocity on his fastball drop nearly a full tick on the radar gun.

But his fastball has never been his strength and has always been hit pretty hard. It was the ineffectiveness of his splitter that accounted for his lack of strikeouts last season. He has had one of the best splitters in baseball, but last year the pitch had just a 16% SwStr% rate (down from 22% in 2023) and it had the least vertical movement that it has had since 2015.

Gausman has reinvented himself before and has been durable throughout his career, so he's certainly a bounce-back candidate. Toronto has been good with getting the most out of its staff. He could be a value around pick No. 180 if he makes the necessary adjustments to his mechanics to fix the splitter. But he's also 34 years old and could be starting the back nine of his career, too, so picking him doesn't come without some risk.

Zach Eflin (-6.9% decline)

Like Gausman, Eflin's big decrease in K-BB% is due to a drop in his strikeout rate. His K% fell from 26.5% in 2023 to just 19.6% last season. But the good news is that his elite walk rate (3.5%) remained intact and he demonstrated some of the best control of any MLB pitcher.

Zach Eflin had a down year.

His strikeout rate plummeted to 19.6 K%.

But the elite control (3.5 BB%) is still there.

Can be a WHIP asset.

Undervalued in @TheReal_NFC.

Currently available at pick 183 in my draft.

— Frank Ammirante (@FAmmiranteTFJ) January 27, 2025

Eflin has never had an overpowering fastball and he relies on his pinpoint control of six different pitches. When trying to ascertain why he struggled to strike out hitters as often, my takeaway is that he leaned more than ever on his sinker and cutter, while throwing fewer breaking pitches. As far as his breaking balls go, he dropped his curveball usage from 27% to 19% while throwing more sweepers last season.

The only problem was his sweeper was much less effective in 2024 with just a 10.6% SwStr% and 28.5% CSW% compared to a 30% SwStr% and 36% CSW% last season.

His numbers in Baltimore were similar to what he did in the first half of the year in Tampa. I'm never excited about a guy with a declining K%, but Eflin has proven he can be effective without striking a ton of guys out, too. Around pick No. 230, he's a very safe pick even if the strikeouts don't come back this season.

The "Not Too Worried" Group

Freddy Peralta (-4.7% decline)

Peralta finished the 2024 year with career highs in starts (32) and innings pitched (173) while going 11-9 for the Brewers. His K% dropped just 3% and his BB% jumped up 1.5%. His 2024 numbers look nearly identical to his 2022 season which was ultimately cut short by injury.

There are still plenty of strikeouts here backed by solid underlying numbers and his slightly high walk numbers aren't enough to cause too much concern. You know what you're going to get with Freddy as long as he stays healthy.

Zac Gallen (-4.0% decline)

Gallen's strikeouts held strong last season as he whiffed 25% of opposing hitters, but his walk rate jumped 3% to 8.7% - his highest since 2021. He missed some time during the year but still managed to make 28 starts for Arizona.

Despite a big dip in innings pitched, Gallen's numbers were pretty consistent across the board and he still managed to go 14-6 for the Snakes with a 3.65 ERA. His career walk rate is 7.8% which is right around the league average, so the walks from last season weren't anything unexpected, just a significant jump from the great control that he showed in 2023.

Logan Webb (-4.7% decline)

Webb's K% dipped a little over 2% and his walk rate returned to his career average of 5.9%. He posted a career-low walk rate of 3.6% in 2023, so what we saw last year was just some regression to the norm. He was a super durable innings eater again in 2024, logging 204 innings over 33 starts and he's now gone over 190 innings in three straight seasons.

Webb is not a strikeout pitcher as he relies on an elite ground ball rate (60.7% for his career) to get outs. What we've seen from him the last few years is what you're going to get and this dip in his K-BB% doesn't signify anything major in terms of the quality of his pitching.

From Average to Bad K-BB% Fallers

Andrew Abbott (-6% decline)

The good news is that Abbott finished 2024 (his sophomore campaign) with a 3.72 ERA and 10 wins. Pitching half of your games in Cincinnati and maintaining an ERA under 4.00 is admirable for sure. But a lot of the underlying numbers suggest that he pitched worse than he did in his rookie campaign and he could be in trouble this year if he doesn't make some major changes.

Abbott's strikeouts evaporated last season as his K% dropped from 26.1% to 19.5%. His walk rate was slightly better but was still nearly 9%. He posted a WHIP of 1.30 for the second straight season and is simply allowing too many baserunners for a fly-ball pitcher who has to pitch in an extreme hitters' park.

Abbott only throws his fastball in the 92-93 MPH range so he relies a lot on his offspeed stuff to keep hitters off balance. He managed to induce a lot of soft contact last year with his breaking pitches, but his swinging strike rate dropped another full tick from 11.9% to 10.8%.

In summary, I just don't think he can keep getting away with how he pitches, especially in Great American Ballpark. His 32% GB% means there are a lot of balls being hit in the air and his 12.5% career HR/FB% is below the league average of 14%. His stats scream regression and he profiles a lot like Andrew Heaney - without the strikeouts.

Jose Berrios (-4.3% decline)

Berrios had an interesting year. He saw his K% drop under 20% to where it was in 2022 - his first full season in Toronto. But unlike that 2022 season (5.23 ERA) - he finished the 2024 campaign with a solid 3.60 ERA which was nearly identical to the 3.65 he posted in 2023.

The good thing about Berrios has been his ability to stay healthy and eat innings. He's made 32 starts in four straight seasons. And his walk rate has remained under 7% in all four seasons in Toronto. But the strikeouts are disappearing from his days in Minnesota when he was up in the 25% range. A BABIP of just .258 last season, an xERA of 4.62, and a FIP of 4.72 all suggest that he overperformed in ERA.

I'd expect his numbers to be worse this year than last, so don't reach for him in drafts just based on his name recognition.

David Peterson (-5.1% decline)

Here's the most confusing guy on the list for me. Peterson's drop in K-BB% is all due to a declining K% as he actually improved his control last season by lowering his walk rate a full percentage point. Peterson had been an over-average strikeout pitcher the last three seasons with a K% in the 24 to 27% range and posted only a 19.8% K% across 121 innings last year.

It remains to be seen if he was more lucky or good last year. He finished with a career-best 2.90 ERA but still carried a 1.29 WHIP. His ERA indicators were all about a full run higher and his HR/FB% of 8.7% is surely bound to regress (his career average is 16.1%).

Even if there's some regression for Peterson here, it doesn't mean that he can't have a solid season and be a very productive fantasy player. But I would exercise some caution here - something isn't quite right as far as how these numbers add up. He's slated to make the Mets rotation to start the season, but remember that he's never thrown more than 121 innings in a season and has a very mixed bag in terms of his history of effectiveness.

Pitchers That Fell Off A Cliff For K-BB%

Griffin Canning (-10.5% decline)

I'm not sure how much space I want to waste on Canning here. Once a promising prospect for the Angels, Canning missed all of 2022 after arm surgery. He returned in 2023 to post a 4.32 ERA and a 26% K% so there was some hope that he still had some potential. But last year he was flat-out awful, finishing with an ERA of 5.19 across 171 innings.

He's in the mix for a long-man spot in the Mets bullpen this year, but I have a hard time seeing him crack the rotation at any point. And he's simply not a guy you're drafting in any format this season.

Jordan Montgomery (-7.9% decline)

Monty had been a reliable arm for three straight seasons while in New York, St. Louis, and Texas. But last year he struggled mightily in his first season in the desert pitching for the Diamondbacks.

His numbers were bad across the board with career-worsts in multiple categories including an ugly 6.23 ERA and just a 15.6% K%. Not only did his strikeout rate plummet, but his walk rate rose to 8.3% as he likely tried to compensate for his lack of whiffs by pitching ultra-carefully to hitters and walking more in the process.

His xERA of 5.46 and BABIP of .351 suggest that hitters were making some incredibly loud contact so we have a really bad situation here where Monty was missing bats less often, walking more hitters, and giving up harder contact, too.

He lost over 1.0 MPH on his fastball and sinker from 2023 and his sinker lost some downward movement, too, as his GB% on sinkers last year dropped to just 43% from 51% a year earlier.

My takeaway here is that Monty was probably always a pitcher who worked on very thin margins. A slight dip in velocity and less command of his pitches resulted in him going from an effective middle-of-the-rotation starter to a guy who was so bad that they had to take him out of the rotation.

Some of his struggles could have been injury-related, but I wouldn't trust him to bounce back this season - at least not to his level of performance from 2021-2023.

Kenta Maeda (-7.4%)

Maeda is back with the Tigers this season but is competing for a job as a long reliever. The 36-year-old pitched 112 innings last year and finished with a 6.09 ERA. His days as a starter in this league are likely over.

Follow me for more pitching breakdowns and keep checking RotoBaller for the latest fantasy baseball advice this preseason!

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