Starting Pitcher "Stuff" Improvers - The Biggest In-Season Risers

March 14, 2023

Jon Anderson looks into the pitchers that most improved the quality of their stuff as the 2022 season went on.

I wrote a post concerning "stuff" metrics a few weeks back. In that post, which you can read here, I went over in short detail what exactly we're talking about. You should read that post first before continuing to get what we're talking about. These are newer metrics and not everybody is familiar, but they are very useful and I think you'll start hearing a lot more about them this season. Today, I want to look at which pitchers improved on these metrics in-season last year. I usually do not write posts like this! I don't like splitting the season into halves and then upgrading pitchers that looked better in the second half than the first. That is because by splitting the data, you are just relying on a shorter sample rather than the bigger one, and the bigger sample will always have more truth to it than the smaller one.

However, with these stuff metrics, that isn't nearly as true. Stuff+ type metrics normalize much more quickly than things like strikeout rate and walk rate. That is because of the granular nature of the metrics. The input data are all single pitches rather than start-level or plate appearance level. This vastly expands the data we're using, because all of a sudden you have 90 or so (one per pitch thrown) data points in a single pitcher start as compared to just one.

Think of it like this: If a pitcher comes up to the Major Leagues and throws one fastball, we can immediately know something significant about that fastball. The next 100 fastballs he throws will almost surely be very similar to the first one. You don't come up and throw a 97-mile-per-hour fastball on pitch one and then a 92-mile-per-hour one on the next. After we see a pitch a couple of dozen times, we can know pretty well about the pitch. That helps Stuff+ stabilize quickly. Before we go further, I have to once again shout out Drew Haugen for developing this model and sharing the data with me, give him a follow ASAP!

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Biggest Starting Pitcher "Stuff" Improvers

A couple more important notes.

First, I did use the traditional "first half" and "second half". Many people will draw a line down on the All-Star Break and compare. I didn't do that. I took each pitcher (15 total starts minimum) and divided their halves individually. So if you made 20 starts, I'm comparing your first 10 with your second 10. It's better!

Second, I am ignoring some of the names at the top of the list because they just aren't interesting. The top three names are actually Drew Smyly, James Kaprielian, and Patrick Corbin. None of those three put up above-average Stuff+ marks even in the second half, so most of their improvement was just because they were so ridiculously bad in their first half. I want to focus only on pitchers I can reasonably recommend taking in standard fantasy baseball leagues. Now, to the names!

Joe Ryan, Minnesota Twins

It still wasn't a great second half from Ryan according to the stuff marks. The 91 mark there isn't great, that's nine points worse than the league average. However, it was good to see Ryan get better late in the year after dealing with some injuries.

In his second half, he threw the four-seamer 61.8% of the time, a really, really high number. The good news was that it racked up a sweet 15.3% SwStr%. He has long been known for getting a bunch of whiffs on his four-seamer, so it seems like something that will stick around. Now we have some reports about Ryan retooling his arsenal for 2023, which could be big for him.

Anything to add on to his solid four-seamer is great, and it was nice to see him take a step forward overall at the end of last year – I think it's a good idea to buy in on Ryan this year, the upside is pretty big even with the discouraging stuff numbers we saw a season ago.

Shane Bieber, Cleveland Guardians

Bieber lost a couple of miles per hour on the fastball last year and that knocked his strikeout rate down to 25% after showing us 30%+ from 2020-2021. He had a quite good season last year even with the lower strikeouts, but you can see that these "stuff" models don't really love how his pitches move.

The good news for Bieber is that his locations and pitch mix are spectacular. He knows how to pitch, he can locate all of his pitches well, and he has several different ways to attack both righties and lefties. Late in the season, he threw more cutters and that seemed to help him. The pitch, for the year, had a strong 13% SwStr% and a great 56% GB%. Bieber is a veteran at this point, but still at the fresh age of 27. He should have a bunch of great seasons ahead, and it was nice to see him be willing to tweak his arsenal and benefit from it.

Blake Snell, San Diego Padres

Snell has never been short for stuff. His four-seamer was strong again, and his slider remained one of the league's best pitches (25% SwStr%). He took it all to a new level in the second half by backing off on the curveball a bit and going four-seamer and slider-heavy. Those two pitches are good enough to make him an ace all by themselves, so as long as Snell is healthy and throwing those two offerings, he's going to have a ton of success.

We saw his ceiling in 2018 when he won the Cy Young. Injuries and command have kept him away from those heights ever since, but last year he reminded us what he's capable of. With a fully healthy season, he has a good chance to earn some Cy Young votes again - and he really doesn't get drafted like that's the case.

Jon Gray, Texas Rangers

Gray had an up-and-down season. He wasn't fully healthy early on and struggled in his first several starts, giving up 14 earned runs in his first four. After that, he got right and pitched very well for his new team.

From May 1st to July 31st, he put up a strong 3.29 ERA with a 1.15 WHIP and ramped the strikeout rate up to 28%. An injury cost him a bunch of time from August 1st to September 12th, and his finish to the year wasn't all that great in the box score (gave up 0, 2, 0, 6, and 3 earned runs in his final five starts).

What we saw with his stuff, however, was great. He was seven points below the average with his stuff in his first 12 starts, and then eight points above the average in his final 12. From July 1st on, he put up a sweet 22% SwStr% with his slider and hitters put up just a .188 xwOBA off of the pitch. All he needs is a decent fastball to go with that great slider, and he's really cooking. The four-seamer wasn't fantastic last year with an 8.5% SwStr% and a 61 Stuff+. He will have to improve on that to really be an ace, but we have seen better stuff from him in the past, and it's exciting to think about what he can do another year removed from Coors Field.

Drew Rasmussen, Tampa Bay Rays

Rasmussen had an impressive year in 2022 with a 2.84 ERA and a 1.04 WHIP. The problem is that the 21.4% K% doesn't really make us believe too vehemently in those numbers. Sure, he had a low 5.3% BB%, but it's hard to put up great numbers with a strikeout rate two points below the league average.

The good news is that the models love his "stuff". He had stuff marks above the league average on all five of his offerings, with the high point being his cutter which he threw 33% of the time and earned a 112 stuff+ with it. The SwStr% on that pitch was 17%, quite high for a fastball, so Rasmussen definitely has something to work with here.

His next most commonly thrown pitch was the four-seamer which earned a 123 stuff+. All of his pitches have merit, and Rasmussen has a lot of weapons to use. The numbers suggest he'll take a step forward in strikeout rate this year, so he's a pretty great pitcher to buy in on while he's still cheap.

Trevor Rogers, Miami Marlins

Rogers was one of the year's biggest busts, but he pitched well at the end of the year and that is going to drag a lot of us back to the table for 2023.

His SwStr% for the year was 12.6%, but over the last two months, it ticked up to 14%. His changeup got right and earned a 20% SwStr% with a 146 Stuff+, and his slider wasn't bad at all either with the same 20% SwStr% and a still good 108 Stuff+. He has the tools, we just have concerns about the command and whether or not he can hold up for another year.

It's hard to feel super excited about Rogers given the inconsistencies we've seen, but there is merit to buying low on him right now.

Bailey Falter, Philadelphia Phillies

Falter was primarily a pitcher that relied on his fielders last season as he threw his (very good) sinker 33% of the time. As with most sinkers, it did not earn many whiffs with a 9.8% SwStr%. A lot of balls were in play off of Falter. In the second half of his year, however, he got more whiffs by prioritizing the four-seamer more. From July 25th on, he threw the four-seamer 46.4% of the time and reduced the sinker to 21%. That resulted in a 12.6% SwStr%, an above-average mark, and the stuff+ model liked the change a lot.

We have to note that Falter might not make the Phillies rotation out of camp, as top prospect Andrew Painter is allegedly being given the chance to take the job. I think Falter gets the first crack at it, but some things are going to happen in his favor for him to stay in the rotation all year. Regardless, he's free in most leagues, so I would be looking to get my hands on him if he is in the rotation on opening week.

Lance Lynn, Chicago White Sox

Lynn has very good stuff. That first half reading was just about him getting back from injury and having a slow start. For the year, he had a 3.99 ERA and a 1.13 WHIP in 21 starts. If we look at his final 11 starts, however, we see a 2.51 ERA, a 1.01 WHIP, and a nice 24% K% to a 3.2% BB%.

His stuff improved as he felt more and more healthy, and we saw that he's still capable of acedom even at the age of 35. He's very cheap this year, and I can't make a good case to not draft him at the current cost.

And that's it. I'm not drafting these guys just because of the stuff improvements as the year went on, but I previously liked them all for other reasons (mostly as buy-low pitchers), so it was good to see them improving late last year in the marks that we can most believe in over short samples. Thanks for checking out the post, come back for more every day!

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