Identifying Breakout Starting Pitchers for Fantasy Baseball Using Stuff+

March 26, 2024

Dan looks at fantasy baseball starting pitcher breakouts and draft sleepers who rate highly in Stuff+ metrics despite not having elite surface numbers.

Just when you thought you had done enough research to prepare for your draft this weekend and considered every available statistic in your process, here comes Thunder Dan with another angle.

I wouldn't be doing my job if I didn't get you to consider which starting pitchers you are going to draft from every possible angle, right? I wanted to discuss some statistics that I haven't used all that much in the past when researching pitchers. I was hoping to gain a fresh perspective on how these stats might better help me (us) understand why certain pitchers thrive while others struggle.

So in this article, I am going to examine three statistics from 2023, Stuff+, Location+, and Pitching+, to see which pitchers, if any, I may have overlooked in my other preseason articles. (Spoiler alert - I landed on several pitchers I already liked but had not had a chance to write about yet - perfect!)

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The Pitching Stats Background

Stuff+, Location+, Pitching+

Let's start with a quick introduction to these stats if you are unfamiliar. I had to do a decent amount of my own research to make sure I understood them at a level that I felt confident in then explaining them to you.

FSWA Hall-of-Famer Eno Sarris and others created these metrics as a way to try and capture the potential effectiveness of every pitch thrown by a pitcher. Stuff+ examines the physical characteristics of each pitch - everything from the velocity to the movement and spin rates - to identify the nastiest pitches, aka, the hardest pitches for hitters to identify and make contact with.

What Stuff+ doesn't measure is where the pitch ends up. That's where Location+ comes in as it measures where the pitcher throws each type of pitch both inside and outside the strike zone. Location+ values change for every pitch and factor in the count (3-2, 1-1, etc) for when each pitch was thrown. The best way I can describe it is "the ability of the pitcher to throw each of their pitches in the ideal spot for that pitch in each situation."

That brings us to Pitching+, which attempts to measure what both Stuff+ and Location+ do and includes the opposing hitters' handedness to give an overall idea of not only how good a pitcher's stuff is, but how good they are at using it.

So why should we care about these statistics? According to Fangraphs, Pitching+ has been a better predictor of future ERA from season to season and is an even better predictive tool for starters in-season once they reach about 400 pitches (about 4-5 starts into the year). Of the three statistics, Stuff+ has been the stickiest from season to season, while Location+ and Pitching+ are more fluid. That makes sense if you subscribe to the idea that pitchers are more likely to improve their control and learn how to pitch situationally from year to year than make big gains in velocity or movement on their pitches.

Let's see if we can use this data to identify some potential breakout candidates in 2024.

Stuff+

Let's take a look at the pitchers with the best "stuff" last year according to this metric. The cutoff I used here was 100+ innings so we would weed out any relief pitchers. I included each pitcher's ERA and K% just to see if we had some outliers.

2023 Stuff+ Leaders

We see quite a few well-known aces on this list who had solid seasons last year (Strider, Glasnow, Cole, Ohtani, Burnes) - pitchers you would expect to see here. One standard deviation for starters is about 12 points and a 100 represents the average. So a Stuff+ rating of 112 or better would be better than about 85% of the starting pitchers in the major leagues. A rating of 124 or more (from Greene on up) would be better than nearly 98% of all starting pitchers.

Graham Ashcraft is a curious case, as his stuff rates out as elite but his ERA is pushing 5.00 and he had a below-average K% at just 17.8%. Ashcraft throws hard (96 mph) but features a cutter, sinker, and slider in his arsenal. He's almost exclusively a two-pitch pitcher as he threw his cutter and slider a combined 90% of the time. His slider checks in at 88 mph, just eight mph slower than his cutter and sinker. What he could really use is a third pitch with a significantly slower velocity (a changeup, per se) to throw off hitters' timing. And his Location+ rating is just 99, which tells us that he's only hitting his spots with his pitches at an average rate. His Pitching+ rating of 103 is good, but not great. He's a bit of an anomaly and not someone we should be interested in unless he makes some major changes to his pitch mix.

It's a bummer that Kyle Bradish had a setback this Spring because he broke out in a big way last season and was a guy that many liked coming into this year.

Hunter Greene is a guy that can be very divisive amongst analysts. He obviously has great stuff, but we have yet to see the results to go with it. It's tough being a fly-ball pitcher and pitching half your games in Cincinnati, that's for sure, and Greene - like his teammate Ashcraft - could really stand to benefit from a solid third pitch. He's been experimenting with a splitter this Spring, but he will need to be able to more consistent in the strike zone with his fastball and slider if he's going to get ahead of hitters and set them up for the splitter down and out of the zone. I'm going to keep an eye on him this year, but I have not been drafting him.

Let's spend some time on Bobby Miller for a minute.

Bobby Miller's six strikeouts. pic.twitter.com/UMMYiycxZy

— Chad Moriyama (@ChadMoriyama) March 18, 2024

I'm on the record being "in" on Bobby Miller this year. He throws every bit as hard as Hunter Greene but has two different speeds of breaking balls and changeup. He rated above average in both Location+ and Pitching+ and yet his 23.6% strikeout rate seems low for a guy with his command and weapons. I think we see him up around 25-26% this season and he cuts that ERA down a half run, too, while winning a bunch of games for what should be the best team in baseball.

Loving Bobby Miller isn't exactly a hot take, I realize that. So how about endorsing an even bigger breakout year for Nick Pivetta in Boston?

Nick Pivetta, Dirty 84mph Slider...and Sword. ⚔️ pic.twitter.com/7T0keDkCI8

— Rob Friedman (@PitchingNinja) March 18, 2024

Pivetta had to work his way out of the bullpen last season and into the rotation, but ended up making 16 starts for the Red Sox and finishing with a 4.04 ERA, 1.12 WHIP, and a massive 31.2% strikeout rate. He saw a nice velocity bump in his four-seamer from 93.4 to 94.6 mph and he features two quality breaking balls of different speeds (curveball and slider). He had a huge increase in his SwStr% in 2023 as he jumped up to 14.5% from where he had been for most of his career (around 11%).

His stuff rates out as well as Miller's and his xFIP of 3.48 last year suggests that he could have some positive regression coming in the run prevention department. A full season of starts could mean 180 innings, 200+ strikeouts, and some very solid ratios. His ADP has been steadily climbing, but at 168 he still feels like a massive bargain for the ceiling he has.

Location+

Here are some quick notes about Location+ before we get to the leaders. The distribution of ratings here is much tighter, though we stick with 100 as the average. One standard deviation is about 3.3 points, so everyone on our list from 107 on up is in the 97% percentile of the metric.

2023 Location+ Leaders

This is a fun list to examine because you see a much wider variety of pitchers and success levels. We have everyone from Ross Stripling and Miles Mikolas to some certified studs like Tarik Skubal and Zack Wheeler. The one common denominator here is a low walk rate (which is why I included it) as the strikeout rates vary quite a bit among this group.

It's no surprise we see two of the best control pitchers in baseball at the top with George Kirby and Zach Eflin. Eflin had a great season and may have even overachieved a bit given his 98 Stuff+ rating. The difference between Kirby and Eflin is only two points, but the gap from #1 to #2 on this list is the same size as the gap from #3 to #12. Kirby was incredibly good last year with a Stuff+ rating of 106 and at his age, could be better yet this season in Seattle.

All five George Kirby strikeouts from today: pic.twitter.com/BKtKaZ1gNv

— Steve (@MarinersSteve) March 11, 2024

The other guys on this list with Stuff+ ratings over 100 are Aaron Nola, Zack Wheeler, and Aaron Civale. Nola could be in line for a bounceback year in terms of his ERA and has been a workhorse in terms of innings and strikeouts regardless. Wheeler is awesome and added a splitter this offseason (which was the en-vogue thing to do apparently). Civale is not a guy you'll hear much about but could be a sneaky good pick late in drafts as he has a bevy of pitches and is a master of painting the corners with all of them.

Pitching+

As I mentioned earlier, Pitching+ attempts to measure what both Stuff+ and Location+ measure separately, but it's not simply a combination of both either. It's an entirely independent metric of its own and is a comprehensive measure of how good a pitcher's stuff is AND how well they are locating it. The variable that isn't measured by any of these metrics is WHEN to throw what pitch in terms of pitch sequencing. Every pitcher has their own learning curve when it comes to learning "how to pitch" or how to "harness their stuff."

The standard deviation here for this metric is around five points. So a score of 105 or better puts you in the 85th percentile and 110 or more (just two guys) in the 97th percentile.

To that end, when we see young pitchers on this leaderboard, it should be cause for excitement.

2023 Pitching+ Leaders

Strider, Wheeler, and Cole are veterans who have it figured out. But there's Bobby Miller and George Kirby again, sitting in third and fourth, respectively. We already discussed them, so let's spend a little time on Bryce Miller!

Miller's rookie season was largely successful, but he still finished the year with a very average ERA of 4.32 and a slightly above-average K-BB% of 17.3%. Like a lot of young pitchers, he was very fastball-heavy in his approach (58%) but got away with it because his fastball was above average in velocity and had good movement. His slider was below-average at generating whiffs compared to other sliders and he experimented with both a sweeper and changeup in search of a third pitch. His Location+ was 104, meaning he was good, but not great at putting his pitches where he wants them and has some room for improvement there.

The lack of an "out pitch" to pair with his elite fastball likely led to his paltry 22% K%. He was simply too good not to strike out more hitters. He's added a split-finger pitch this offseason that could help tremendously if it's any good - which stands to be seen. At only 25 years old, Miller is oozing with potential and still being drafted around pick 180. Something tells me he's going to take a jump in strikeouts this year and end up being a pretty good bargain at that ADP.

Last but not least we should probably talk about our cover athlete - Grayson Rodriguez.

Gray-Rod had an uneven rookie season that saw him get demoted to the minors after a rocky start, only to return and pitch extremely well down the stretch.

He's at the tail end of both our Stuff+ and Pitching+ leaderboards with a Location+ rating of 102. Location was clearly a big issue with Rodriguez in the early going last year as he was leaving way too many pitches in the middle of the zone. After making some adjustments at Triple-A, Rodriguez pitched from July to October to the tune of a 2.58 ERA and 1.10 WHIP. He cut his walk rate down from 10% to 7% and finished with a solid 25% K%.

Min 100 pitches, spring Stuff+ leaders (not all parks have statcast)

1) Luis Gil 139
2) Jared Jones
3) Grayson Rodriguez
4) Jorge Alcala
5) Eury Perez
6) Wes Parsons
7) Miguel Castro
8) Josh Winckowski
9) Bowden Francis
10) Casey Mize 110https://t.co/qHIcgT6usT

— Eno Sarris (@enosarris) March 15, 2024

Rodriguez features a 97 mph fastball, two breaking balls, and a change-up. If he develops the command this season that we often see from young pitchers who are gaining more experience, he could be primed for a big year. Most projection systems have him cutting at least half a run off his ERA while maintaining high strikeout numbers. The industry is already very high on him with an ADP of 71, but there's still some room for profit if you want to take him a full round earlier. He has the makeup of a superstar pitcher and a chance to win a bunch of games for what should be a pretty good Baltimore team.

Okay, that's it. I'm done writing about pitchers this preseason. Good luck in your drafts and in your leagues this year!

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