Validation

Adair has tightened up French's slider-Johnson said it was day and night....

-Shannon Drayer

We hate drawing conclusions based on a sample of one game. Lucky for us, Rob Johnson is here to draw a conclusion for us, making our job much simpler.

Experiment: Lucas French's slider was different yesterday than in previous starts.

Null Hypothesis: Lucas French's slider showed no meaningful difference in movement.

Means of testing: pitch F/X data.

Any objections? No? Good. Lets go to the data then. Here is the breakdown of pitches determined to be sliders, and only sliders, by MLB's pitch classification.

French_medium

10 August has an asterisk by it because that game was caught by Kenji Johjima. Hence why I included two total lines, one an average of all sliders caught by Rob Johnson and one an average of all sliders thrown by French as a Mariner.

Once again, we are dealing with sample sizes that are just way too small to make any sort of declarative statement. That being said, we are only looking to examine Johnson's categorization of the pitch as a "night and day" difference. What do the numbers seem to say? Well, it is not real clear cut.

On one hand, if you took the average of sliders compared to the sliders thrown on 21 August, the best you could say was that they were slightly faster. A 2mph difference is hardly an amazing feat. He did throw them for more strikes, but because of the sample size we are dealing with, we're talking about throwing a strike 11 times out of 17 instead of 10. Maybe Rob Johnson has a deft feel for small percentages.

However, if you want to simply look at the comparison between 15 and 21 August, a lot more stands out. First, back to speed, the difference is almost 5mph, which is noteworthy. A bigger and likely more noticeable trait for a catcher though is the vertical movement, which increased an average of over two inches from his the 15th to the 21st. Is that what Johnson was referring to?

Maybe, but then again, pitch F/X has just seven sure sliders thrown in the start of the 15th. It does has 11 "cut fastballs" thrown as well, which kind of look like French's slider (see image below fold). Pitch typing on pitch F/X is an ongoing math problem amongst analysts, and frankly, I would call all of the "cut fastballs" as sliders except for a few that are clearly actually fastballs based on their movement and/or speed.

If you do classify French's cut fastballs (the non-fastball ones) as sliders, you get these new averages:
15 August -- 0.02 horizontal movement -- 4.08 vertical movement
21 August -- 0.06 horizontal movement -- 4.31 vertical movement

Can Rob Johnson tell the difference between 0.04 inches of horizontal and 0.23 inches of vertical movement six days later? I bet not. You know what I bet Rob Johnson did notice? That six of Lucas French's sliders yesterday resulted in a swing and a miss compared to zero on 15 August.

The results were night and day, not the pitch itself.

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