2020 Forecast — Starting Pitcher K% Surgers, A Review

Let’s move over to the pitching side where I’ll start my 2020 forecast reviews with strikeout rate, or K%. As a reminder, there is never, ever, ever a reason to evaluate K/9 instead of K%. A denominator based on outs is at risk of being heavily influenced by BABIP, walks issues, field errors, HR/FB rate, etc, because higher numbers in those metrics extend innings and result in additional batters faced, giving the pitcher more opportunities to strike out a batter, even though the denominator has remained the same. That can’t happen when your denominator is total batters faced, like in K%, as more batters faced in an inning will reduce K%, as it should, as opposed to having no effect on K/9.

With that out of the way, let’s review my starting pitcher K% surgers published in mid-Feb, which used my pitcher xK% equation, and highlighted four fantasy relevant starters whose xK% marks were significantly higher than their actual K% marks. Obviously, a higher xK% doesn’t automatically mean the pitcher’s K% will rise the following season, as the underlying metrics driving xK% could change. But it does offer optimism that if the pitcher merely maintained those skills, better luck or sequencing could yield a higher strikeout rate.

K% Surgers
Name 2019 K% 2019 xK% Diff 2020 K% 2020 K% – 2019 K%
Justus Sheffield 22.0% 25.2% -3.2% 20.7% -1.3%
Zach Plesac 18.5% 21.0% -2.5% 27.7% 9.2%
Patrick Sandoval 24.9% 27.3% -2.4% 20.8% -4.1%
Dylan Bundy 23.1% 25.5% -2.4% 27.0% 3.9%

So the list went 2 for 4, but the two wins represented big breakouts and fantasy values, while a third loss actually posted strong results, despite skills not backing up those results.

Justus Sheffield was one of my favorite starting pitcher sleepers heading into the season thanks to a strong SwStk%, fueled by an elite slider/changeup combination. His xK% suggested better things were coming, so combined with his ground ball tilt, I was buying him everywhere. Unfortunately, both those weapons lost significant whiffiness and his overall SwStk% dropped precipitously, bringing his strikeout rate down marginally. If you were an owner all season, it didn’t really matter though as he benefited from some incredible HR/FB rate luck to push his ERA down nearly two full runs, and make it appear like this was the breakout I was calling for. It wasn’t. Now I don’t know which was closer to the real Sheffield, the exciting two-pitch combo we saw in 2019, or the blah mix we saw in 2020. Either way, his price has likely risen far too much given the sparkling 3.58 ERA for me to roster him this season.

Zach Plesac is a perfect example of why any xEquation cannot simply be blindly followed as a guide for your next season projection. His 5.13 SIERA in 2019 suggested he would be worthless in leagues in 2020 and someone to avoid, especially as fantasy owners looked at the 3.81 ERA and thought he would be a good buy. The thing is, that SIERA is built on a pedestrian 18.5% strikeout rate, which xK% says he deserved better then. So once you adjust his 2019 performance to reflect the better strikeout rate, then consider his strong minor league strikeout rates, Plesac suddenly moved out of “avoid” and became someone to actually consider rostering. He also threw his changeup and slider more at the expense of his fastball, which is usually a good move for a pitcher’s strikeout rate, and worked out thrillingly here. Obviously, don’t bet on this performance again, as a 2.9% walk rate is reallllly hard to maintain, while no one is .224 BABIP good.

Along with Sheffield, I was a big fan of Patrick Sandoval heading into the season thanks to his elite changeup. While his slider and changeup remained elite, his weak fastball generated an even lower rate of swings and misses and his strikeout rate fell. However, he owns a high ground ball rate, but was done in by a ridiculous 32.3% HR/FB rate. A 4.17 SIERA suggests there’s still potential here if he’s given another shot at the rotation. Don’t forget about him in deeper leagues.

Dylan Bundy was the second big breakout this list nailed, as his strikeout rate surged to a career high, despite him posting an identical SwStk% to 2019. He also benefited from a career best HR/FB rate, which was cut in half after getting out of Oriole Park. I am concerned, however, as his velocity graph looks ominous. Over his last two starts, he failed to average 90 MPH with his fastball, while he finished the season at just 88.6 MPH. It’s certainly sensible that we should give him a pass here given the delayed season and the possibility that he wasn’t able to build up his arm strength and stamina as he normally would in regular seasons. But given his breakout and likely price jump, I’m inclined to play it safe and let someone else gamble either that his velocity rebounds or that a sustained velocity decline won’t hamper his results.





Mike Podhorzer is the 2015 Fantasy Sports Writers Association Baseball Writer of the Year. He produces player projections using his own forecasting system and is the author of the eBook Projecting X 2.0: How to Forecast Baseball Player Performance, which teaches you how to project players yourself. His projections helped him win the inaugural 2013 Tout Wars mixed draft league. Follow Mike on Twitter @MikePodhorzer and contact him via email.

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I’ve found this to be my go-to leaderboard for K% expectations: https://tinyurl.com/ShadowWhiff

Seems like most of the successful strikeout pitchers get whiffs around the edge of the zone. These are nearly 50/50 pitches by definition (51.6% of taken pitches in this zone were called balls last year), and wOBA for pitches put in play in this zone had a .333 wOBA last year versus .369 wOBA for all balls in play. If you can get whiffs on pitches that are (a) called balls half the time or (b) not very valuable when put in play (for reference, Aaron Judge overall wOBA 2020 was .368, Kyle Seager overall wOBA 2020 was .333) in case they do get hit, then you’re doing something right.