St. Louis Cardinals: Imagining An Expanded Repertoire For Luke Weaver

Aug 20, 2016; Philadelphia, PA, USA; St. Louis Cardinals starting pitcher Luke Weaver (62) pitches against the Philadelphia Phillies during the first inning at Citizens Bank Park. Mandatory Credit: Bill Streicher-USA TODAY Sports
Aug 20, 2016; Philadelphia, PA, USA; St. Louis Cardinals starting pitcher Luke Weaver (62) pitches against the Philadelphia Phillies during the first inning at Citizens Bank Park. Mandatory Credit: Bill Streicher-USA TODAY Sports /

St. Louis Cardinals pitching prospect Luke Weaver is hoping to expand his repertoire by adding a sinker.

Just before the start of St. Louis Cardinals Spring Training, Jenifer Langosch reported that Luke Weaver was working to expand his repertoire. Specifically, she reported Weaver wants to add a sinker and slider.

I’m admittedly wary of the slider. Keith Law noted that Weaver has never had a breaking ball of any kind, even in college. Additionally, Baseball America made no mention of one in their report upon Weaver’s call-up last season. Maybe Luke Weaver will throw a fine slider, but there’s no way to know what it will look like as of now.

We can, however, get a picture of what a Luke Weaver sinker might look like, despite the fact that he’s never featured one in his repertoire. As it turns out, the spin rate and movement of a player’s fourseamer is highly correlated with the spin and movement on both a cutter and sinker.

In his debut season with the St. Louis Cardinals, Luke Weaver already featured a fourseamer and flashed a cutter. The addition of a sinker would put him in a small club. Over the last two seasons, there were nineteen pitchers who threw a fourseamer, cutter, and sinker each 100+ times in the same year, six of which did so in both 2015 and 2016 resulting in a sample of twenty-five seasons.

I was initially worried that the mechanics of throwing a cutter or sinker might differ significantly from a fourseamer. To address this, I looked at spin rates. I found that fourseamer spin rate correlates extremely well with cutter spin rate, and reasonably well with sinker spin rate. This indicates that the mechanics of throwing these types of fastballs does not significantly differ.

So, this is a positive sign that, despite rarely throwing a cutter or sinker before 2016, Weaver should be able to develop these pitches quickly heading into 2017. Next, I looked at how fourseamer movement translates to cutter and sinker movement.

Cutter movement is much harder to predict from fourseamer movement. Luckily, though, we have the cutters Weaver threw in 2016 to work off. Sinker movement is much more closely correlated with fourseamer movement, so we can use that to predict what a Luke Weaver sinker will look like using the equations listed in the charts.

Note that for a right-handed pitcher, a negative value for xMov indicates arm side horizontal movement. A positive zMov indicates “rise,” and the lower the zMov the further the ball is sinking. Overall, his fourseamer/cutter/sinker repertoire might look something like this.

A few things immediately jump out. First, Weaver already generates greater than six inches of run on his fourseamer. Comparing that with the 139 pitchers who threw fourseamers and 100 innings last season, Weaver ranks in the top 20% for arm-side run. Consequently, I estimated his sinker would get about twelve inches of arm-side run.

Even if the movement doesn’t translate perfectly to his sinker, he should still generate more arm-side break on his sinker than most other pitchers. If the movement does translate, the break differential between might be more than a foot.

Additionally, Weaver gets less rise (or more sink) on his fourseamer than most other pitchers. In fact, he’s in the lowest quartile for fourseamer zMov. This lends itself well to a groundball repertoire. That movement should translate well to a sinker and, to a slightly lesser extent, his cutter.

Mike Matheny has also taken notice, according to Jenifer Langosch. When asked about how Weaver’s fastball and sinker could complement each other, Matheny said it should work well, “especially with as much sink as he has.” If you don’t trust the numbers, maybe you’ll trust the long-time catcher-turned-manager.

While the result might look like an uninspiring repertoire, Kyle Hendricks broke out in 2016 featuring a similar array of fastballs (though he didn’t throw enough fourseamers to meet my qualifications). Hendricks, of course, has been the focus of the pitch tunnel research over at Baseball Prospectus.

The pitch tunnel concept suggests that pitchers can deceive hitters by throwing pitches that look almost the same at the point where the hitter must decide to swing or not, and that break substantially enough after that point to either induce weak contact or miss the bat entirely. While this wasn’t quantified until recently, both Greg Maddux and Tim Hudson built careers based on this idea.

Here, you can see Hudson facing Corey Seager back in 2015.

On a 1-0 count, Hudson tried to get Seager to bite on a sinker that started over the corner and broke off the zone (red trail). Seager laid off, and Hudson battled him to a 3-2 count. Hudson then turned to a cutter (purple), which he started in the exact same spot as the sinker. Except the cutter held on to the corner, and by the time Seager would realize he needed to swing, it was too late.

Luke Weaver has already shown that he has at least some understanding of the tunneling concept. Check out this sequence against Oakland slugger Khris Davis:

Weaver started the at-bat with a cutter (blue) that started toward the corner before darting just off the plate. Then, with the count at 2-2, Weaver starts a fourseamer (pink) on a nearly identical line and tails it back just enough to catch the corner for strike three. By the time Davis realized he had to swing, it was too late.

There was a horizontal break differential of exactly 5.39 inches between this cutter and fourseamer. Now imagine what Weaver could do using a sinker with twelve inches of run that looks like both the cutter and fourseamer out of his hand.

Good luck.

Luke Weaver was known primarily for his command while in the St. Louis Cardinals farm system. If he can develop a fourseamer/cutter/sinker combination and control it well enough to consistently hit the corners, Weaver could become a weak contact machine.

He already has the makings of a groundball pitcher with the sink on his fourseamer. Translating that downward plane to his cutter and sinker would net him a ton of groundballs. The deception in the repertoire should results in a fair number of strikeouts.

There’s obvious precedent that this repertoire can be both highly successful and sustainable. It could very well turn Luke Weaver into a dependable number two or three starter for the St. Louis Cardinals in the next few years.

Next: Luke Weaver Leaves Game With Trainer

Credit to @cardinalsgifs for the top-notch editing of the GIFs included in this article.