Unlocking James Paxton

Theory: the Mariners want to be good soon. I haven’t talked about that with anyone in the industry, so I might be way off, but it’s the assumption I’m going to work with. Another assumption follows: if the Mariners want to be good soon, they probably figure James Paxton could and should be a part of it. The Mariners, probably, want Paxton to become a major contributor as soon as the season ahead. Toward that end, Paxton needs to stay healthy, and the healthy version of Paxton needs to do better.

There’s nothing worth saying about Paxton’s health. Hopefully he doesn’t get hurt. I don’t know why he gets hurt, and I don’t know how he can stop. You cross your fingers. But as far as being better is concerned? Most everything comes down to mechanical repetition. And health, of course, plays some role in that. Out of more consistent mechanics, the Mariners would like Paxton to improve his location. They’d like him to improve his changeup. And there’s another idea, which I already wrote about once some months ago.

In the dead of last winter, I put some numbers together, and I came away believing that Kevin Gausman and James Paxton might be able to benefit from throwing more high fastballs. Gausman and Paxton, in 2014, consistently kept their fastballs down, but they were also fastballs with a certain type of spin, fastballs that you more typically see higher. They threw their fastballs like they were sinkers. It didn’t make them awful or anything, but it made them hittable. I saw some strikeout potential hidden in the fastball location.

This past season, Gausman started flirting with more fastballs up in or beyond the zone. It was a deliberate adjustment. Paxton, though, didn’t change a thing, as his fastball was concerned. Of course, he also got hurt and missed a bunch of time, but when he was playing, his fastball was as low as ever. Which made it as unusual as ever. Interestingly, some of the groundballs also went away, but let’s not get derailed. I’m going to show you a table, pulling data from Brooks Baseball and the Baseball Prospectus PITCHf/x leaderboards. In this table, you see Paxton’s average 2015 four-seam fastball, and then you see the eight most similar lefty four-seam fastballs, based on speed and movement. If you remember when I would experiment with pitch comps, these are the eight lefty four-seam fastballs with comp scores no greater than 1.0.

I’ll explain some of the table after the table!

2015 Four-Seam Fastballs
Pitcher FA Velo H Mov V Mov Contact% Height High FA%
James Paxton 95 6 10 88% -5.6 22%
Kevin Siegrist 95 7 10 74% -1.8 29%
David Price 95 7 10 74% 0.6 37%
Cole Hamels 94 7 10 83% 1.9 39%
Ian Krol 94 7 10 82% 4.3 53%
Glen Perkins 95 7 10 84% 3.5 49%
Adam Liberatore 95 6 9 78% 0.4 38%
Jake McGee 96 7 10 74% -0.8 35%
J.A. Happ 93 6 10 80% -1.4 30%
non-Paxton average 94 7 10 79% 0.8 39%
SOURCE: Brooks Baseball, Baseball Prospectus

Paxton, eight other names, and an average of those eight. You see average fastball velocity, average horizontal movement in inches, and average vertical movement in inches. Then there’s fastball contact rate, and height, in inches, relative to the vertical middle of the zone. The lower the number, the lower the average fastball location. The last column is related: this shows the rate of fastballs thrown in or beyond the upper third.

The basic idea is this: location tends to follow vertical movement. The lower the average vertical movement, the lower the average location. These are sinkers and two-seamers. The higher the average vertical movement, the higher the average location, most of the time. These are your four-seamers. Paxton shows up with a fairly high vertical movement. Put another way, Paxton generates a good amount of backspin. He throws a fastball you expect to be thrown higher. He’s very rarely elevated it.

Look at the table. Paxton threw the lowest average four-seam fastball, and it follows that he had the lowest frequency of fastballs up. Compared to the other eight, Paxton’s average fastball was more than six inches lower. And he threw 17 fewer high fastballs per 100. Perhaps not coincidentally: Paxton also shows up with the highest contact rate. Fastball swings and misses tend to be up. Paxton didn’t throw the ball up.

For this, I’ll pull from Baseball Savant, and I’ll just show you Paxton’s whole career, instead of just 2015, so as to boost the sample size. You see where Paxton has located his fastballs, and you see — on the right — which fastballs have missed bats.


I think it’s pretty telling. A lot of those whiffs have been on fastballs up. Down, you get more contact, or balls. There’s nothing wrong with generating a fieldable grounder, and Paxton’s had some good stretches of that, but he allows too much contact for a pitcher with his stuff, and he issues too many walks. Ultimately the very most important thing is just command, but if Paxton were to throw his fastball to less predictable locations, the pitch itself could miss more bats, and it could allow for his other pitches to also miss more bats, as hitters wouldn’t be able to all but forget about the upper half.

In the earlier table, I compared Paxton to eight other fastballs from just 2015. When I looked at the whole PITCHf/x era instead, I still found Paxton with a far lower fastball whiff rate than his peers. Sean Doolittle shows up as a fastball comp. And as a related attempt, I took 2015 four-seam fastballs, thrown by both righties and lefties, and I sorted by vertical movement. Then I averaged the 10 pitchers above Paxton and the 10 pitchers below. That group threw its average four-seam fastball more than six inches higher than Paxton did, and it also had an average fastball contact rate south of 83%, while Paxton was a bit north of 88%. That might seem like a small difference, I don’t know, but it’s really five or six extra whiffs per 100 fastballs. The average game features something like 60 fastballs.

The takeaway isn’t complicated. I’m not saying this is the whole key to James Paxton’s potential, but it seems curious to me he throws his fastball so low, when his peers with similar fastballs use theirs higher on average. Those same peers miss more bats, and Paxton isn’t hurting for any velocity. And if you’re afraid of high fastballs getting hit for homers, Paxton’s also in a forgiving ballpark a lot of the time. It’s a bit less risky than it might be for a Kevin Gausman in Baltimore. Pitching isn’t this simple, but I do believe Paxton would benefit if he could throw more fastballs up.

Early in the year, Paxton told Eno he had the high fastball on his mind. Not much happened differently. But a month ago, there was this note:

“I’m working on some really good things,” he said. “I’m trying to implement my high fastball a little more. My changeup is taking strides. I’m really happy with the progress I’m making. It’s interesting, because I’ll get to a count where I think it would be a perfect place for a curve or cutter, but it really forces me to focus on fastball location and my changeup. I think it’s really going to help me.”

We’ll see if this happens. We’ll see if Paxton works up in the zone more often. And we’ll see if it helps. It’s not like we can know anything today. If Paxton struggles to locate, he’s probably doomed no matter what. But I think there’s something here. He has the raw stuff to be a strikeout-an-inning starter. All he might have to do is use it right.

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Jeff made Lookout Landing a thing, but he does not still write there about the Mariners. He does write here, sometimes about the Mariners, but usually not.

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Adam Symonds
Adam Symonds

Reading old Rick Waits and McClendon articles, it seems plausible Paxton and Walker were both being encouraged to throw low fastballs to increase GB rates. DiPoto’s statements about fly ball pitchers in SafeCo after the Karns trade may bode well for a shift in emphasis on Paxton’s four seamer. One can hope, anyway.