You hear it all the time. “His fastball is too straight.” “His fastball has really great run to it.” “He gets some great arm-side movement to his fastball.” “He really needs to work on getting some movement to his 4-seamer.”

It’s something that scouts and hitters and broadcasters and coaches and front office personnel have been saying since forever. I fell into this trap myself for the longest time. Whether it was as a pitcher myself, or when the Royals drafted Singer in the first round back in 2018, I always just assumed that having run on your fastball was better than throwing it in a straight line to your catcher.

It makes sense, right? The more your ball moves, the harder it is to hit. That’s why people throw curveballs and sliders. The pitch moves and therefore makes it harder to hit. The same logic ought to apply to fastballs as well, right?

No, actually.

There are currently 352 right-handed pitchers in MLB this season that have thrown at least 100 total pitches and 50 total fastballs (of any flavor: cutter/sinker/2-seam/4-seam). Only 28 of those pitchers have thrown more fastballs than Brady Singer in 2020, and Singer gets better arm-side run than most (pictured: Singer and another Royals with great run, Jesse Hahn, shown in comparison with guys who throw lots of cutters, Alex Colome and Kenley Jansen).

As you can see, there is no correlation between a pitcher’s ability to create arm-side run with his fastball and his ability to generate swings and misses with the pitch. If anything, the data actually suggests that pitchers who can cut the ball away from right-handed hitters/into left-handed hitters will generate more swings and misses.

Since the beginning of the 2019 MLB season, 504 RHP have thrown at least 250 pitches and at least 100 fastballs. Here is how the horizontal movement of those pitchers compares with their Swing & Miss%:

The correlation actually grows stronger as we back up and 2019 into the equation. Here’s adding 2018, minimum 500 total pitches and 250 fastballs:

Again, if anything, the data suggests that having arm-side run on your fastball, if you’re a RHP, is counter productive to the goal of missing bats.

Missing bats isn’t always the only objective, to be fair, so we’re going to run the same exercise with the next most important objective, which is generating weak contact. Here’s 2020:

2019 and 2020:

2018, 2019, and 2020:

Again, all of the data would actually suggest there is absolutely zero correlation between getting good, arm-side run and having success with your fastball. Maybe they generate more ground balls?

Nope.

The three most important things that a pitcher can do with any pitch, in order, are as follows:

1. Get the batter to swing and miss. If they can’t hit the ball, they can’t score runs.
2. Get the batter to hit the ball softly. The softer they hit the ball, the more likely you are to get an out.
3. Get the batter to hit the ball on the ground. They can hit it 400 mph. If it bounces, it can’t be a home run.

Today we have seen that there is absolutely no statistical correlation between a RHP’s ability to generate arm-side run and having success with that fastball. Here’s the good news, however: the data isn’t strong enough to imply doom on Brady Singer either. Gerrit Cole and Kirby Yates both generate well better than average arm-side run and generate a ton of swings and misses. Gerrit Cole might even be the best pitcher in baseball.

My only real point in all of this is this:

Stop worrying about a pitcher’s (specifically RHP) fastball being too straight. The data suggests that throwing the ball straight as an arrow can actually be more beneficial than letting it run into a RHH’s barrel. Also, it may be in the best interest of Singer and all young pitchers to learn a cutter, and for organizations to stop putting so much emphasis on pitchers’ ability to make their fastballs run.

(For the record, the same with all of this is mostly true for LHP but they mess up the graphics because their arm-side run is a cutter for RHP. Anyways, as you were.)

Thanks for coming to my TED Talk.

Photo Credits: Charlie Riedel.