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Expectations for Jack Flaherty and Sandy Alcantara

Two young pitching prospects and what their stats say about their future

MLB: St. Louis Cardinals-Media Day Steve Mitchell-USA TODAY Sports

Jack Flaherty and Sandy Alcantara are two prospects to watch in 2016. Both were only 20 years old, but had good results in High-A last year. Flaherty spent the whole season there, throwing 134 innings at 8 12 strikeouts per nine, and 3 walks per nine. That came out to a 3.20 FIP, above average for the level while being younger than average. Alcantara spent most the season at Full-season A, one step below. He both struck out and walked a bunch, 12 per nine and 4 12 per nine respectively. He moved up to High-A for 32 13 innings, stiking out a little more than one hitter per innings, while walking nearly 4 per nine.

Both were rated well by resident prospect specialist The Red Baron. Alcantara was ranked 9th, with Aaron enamored by the fastball. While he throws a curve, Aaron thinks a slider would work better with his three quarters delivery, and he sees a future average changeup as well. Flaherty ranked 5th. Nothing jumps off the page for him, but Aaron sees the potential for three 55 pitches, and combined with above-average command, that’s a pretty effective arsenal.

Generally, what the scout see is what matters in the mid-levels of the minors. However, it doesn’t have to be the only thing. We can learn a little more about these players by looking at the numbers. As I mentioned, both were 20 years old in 2016. First, I wanted to just get a general idea for how production in High-A translated to big league success. Using the leaderboards at Fangraphs, I found every case of a 20 year old who threw at least 30 innings at High-A. I then matched that up with every case in which the pitcher threw 30 innings in the majors as a starter in their age 21, 22, and 23 seasons. I then took the difference in their FIPs, and found an average for each set. Lastly, I applied that average difference to Alcantara and Flaherty’s High-A FIP. Here’s the results:

For context, average FIP in 2016 was 4.30. Alcantara grades out really well here, but he also managed to not give up a single homer in his time at High-A, and the team’s home ballpark is known for being pitcher friendly. Alcantara’s stuff is probably tough enough that hitters just have trouble squaring it up, but there’s still a good amount of noise in such a small sample.

This group saw a big jump in performance from 22 to 23, though with the sample sizes I’m betting a good chunk of the difference is noise. According to my average aging curve for MLB pitchers, 23 year old pitchers gain 0.3 WAR/200 innings compared to their age 22 season. That’s a sample of 53 players, a little more than the samples above. There’s surely a bias to these numbers: not every 20 year old High-A pitcher becomes a major league starter. The numbers here reflect the gains of a subgroup of High-A 20 year olds who performed well enough to become major league starters one or two or three years later. At the least, Flaherty and Alcantara did perform better than average starters for 20 year olds who spent time at High-A.

The problem is, minor league FIP probably isn’t the stat we should be looking at. It doesn’t correlate as strongly with future Major League FIP as other stats. Here’s a scatter plot for 20 year old High-A pitchers to 22 year old MLB pitchers:

That’s a pretty low R squared value. What is more meaningful, but still not all that meaningful, is K%:

Again, not a strong relationship, but something is there. As you might have guessed, walks aren’t very meaningful:

That’s pretty close to random. At these samples and correlations, you can’t draw firm conclusions. Still, I like that this result, as it jibes with scouting assessments: for minor leaguers, particularly the low and mid levels, usually a scout cares much more about missed bats than avoiding walks. Pitchers can improve command over time, they usually don’t improve their stuff more than marginally.

I also took a look at K-BB%:

K-BB% is just barely more predictive than K% on it’s own, at least for this sample. That makes sense, since walks had little predictive value. At these sample sizes though, we don’t want to read to much into the idea that walks have almost no affect.

Using the best fit lines from the graphs above, and their High-A stats, I calculated expected FIPs for Alcantara and Flaherty:

Again, with such a low R squared value, we don’t want to take these too seriously. They’re more like broad over/unders. On average, players with Alcantara and Flaherty’s strikeouts and walks, they project to be slightly worse than average MLB starters. While it’s not usually why we watch baseball, there’s value to that. There’s also a large variance attached to that, so it’s not like we’re just penciling in these two to be 4th or 5th starters a couple years from now. Maybe they turn into 2nd or 3rd starters, maybe they don’t make the show at all or don’t hang around long. Again, think of it as a broad over/under, and only in the case that they do make the majors.

We can’t all be great scouts, and even if we were, we might not have much time to watch minor league games. A lot of us generally take the opinion of the scouts we trust, and supplement that by scouting the stat line. If we’re going to do so, we might as well have a better understanding of what stats we should be scouting.

There’s a lot more ways to improve this. Aggregating performance over years and getting a better idea of bust rates to name a couple of the more glaring omissions. I certainly plan on making this better going forward. This is just a quick dip into the world of scouting the stat line, but we already have some data that agrees with the scouts: missing bats is generally a better indication of a prospect’s future than their results. At least in the case of 20 year old High-A pitchers. That’s a really good thing for Alcantara, and more of a wash for Flaherty.