Tommy Joseph: Age 19 in the Cal: League Avg. or Mastery?

Tommy Joseph: Age 19 in the Cal: League Avg. or Mastery?

Understanding Trendlines & Within-Season Variation for Prospects

Tommy Joseph has been the subject of a lot of sample size parsing this season. He posted a Dr. Jeckyll and Mr. Hyde type season at San Jose in the Cal:

Apr-Jun 309 0.234 0.282 0.362 0.644
Jul-Sept 261 0.315 0.368 0.618 0.986
Total 570 0.271 0.321 0.478 0.799

Some people look at that second half line and drool. Others see the full line and say, decent season, but it was the Cal. You can't just pick and choose your sample sizes to fit your story.

The counterargument to that is commonly: He improved! He learned! That's why his second half stats are better.

But is that a valid argument? If so, we would expect to see continual, gradual improvement, not just a huge second half jump. If we can show that, it would be a big step towards pointing at certain areas of his game, and saying, this is where he improved during the season.

So let's take a more in-depth look at his season via rolling averages.

I decided to first look at what window would be most useful:

10-game moving averages:


20-game moving averages:


30-game moving averages:


60-game moving averages:


I settled on the 30-day moving average. The 10 and 20 day averages have too many troughs and valleys, and the 60-day is too smooth.

As we can see in all the charts above, after a hot initial start, Tommy slumped massively, and then he gradually improved throughout the season. The next question is, where did he improve?

Let’s look at the stats broken down into K%, BB%, BABIP, and PF. PF is power factor and is defined as TB/H. I like these four buckets, because they are all separate. In a plate appearance, he either K’s, BB’s, or puts the ball in play. If he puts it in play, BABIP tells us whether it’s a hit. Once it’s a hit, PF tells us how hard he hit it.

I use PF/10 below because I couldn’t figure out how to get Excel to do a multi-y-axis graph.


He learned to strikeout less. He started the season up around 20% and ended it around 17-18%. Perhaps he got better at making contact and fouling off pitches, or perhaps he learned to layoff pitches.

He hit the ball slightly harder as the season went on, too. He hit 1.5 total bases/hit in May, and ended up around 2 total bases/hit in September. 1.5 is a good PF. 2.0 is elite.

His BB% didn’t change much, however, until the very last two months. It stayed at 5% throughout the season until August and September where it gradually started to climb. He ended the season with a 7.2% walk rate. Whether that’s due to actual increased patience on his part or pitchers pitching around him, we can’t say.

Finally, his BABIP climbed enormously. He went from a low of .200 BABIP during his slump to ending the season consistently above .400 BABIP. He learned to recognize pitches and make good contact with the pitches he put into play. In essence, he out-leveled the league. The BABIP chart clearly shows that the CAL league initially was too hard for him as a 19 year old. He couldn’t handle the pitching. He K’d a bit more, but not excessively more than he did at the end. He didn’t change his patience profile. He would connect with a good pitch every once in a while and send it into the stands, but on many pitches he was just overmatched. But he adjusted, and as he adjusted he learned to hit more pitches with more authority. More of these pitches turned from soft popups and soft grounders into line drives and long fly balls. Eventually, he outmatched the pitching in the league.

In the majors, only the elite hitters have a BABIP over .350. In the minors, a BABIP above .350 means that the prospect overmatches the pitching. He hits more pitches with better contact producing more LD’s, HR’s, etc. I would categorize his season last year as much more than simply a "league average" season. He mastered the pitching by the end of the season, and moreover, he showed tremendous ability to learn in-season. Seeing Tommy master Cal league pitching as he turned from 19 to 20 is enormously impressive and heralds great things for his future.

This FanPost is reader-generated, and it does not necessarily reflect the views of McCovey Chronicles. If the author uses filler to achieve the minimum word requirement, a moderator may edit the FanPost for his or her own amusement.

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