With Mike Leake no longer a member of the St. Louis Cardinals, a permanent rotation spot has seemingly opened up for the 24-year-old Luke Weaver. I use the qualifier “seemingly” because other options exist should Weaver falter. Fortunately, this has not been an issue for Weaver just yet (small sample size alert!), posting a 0.7 fWAR over 29.0 innings pitched. For perspective, Leake put up 1.9 fWAR through 154.0 IP as a member of the rotation. Of course, WAR is not a statistic that only increases, but Weaver is off to a tremendous start, nonetheless. So, how is Weaver — considered a future reliever by many — succeeding as a starting pitcher? It undeniably helps having his last two starts against the Brewers (92 wRC+) and Padres (83 wRC+), but even bad teams can jump on subpar pitching.

Let’s begin by taking a closer look at Weaver’s repertoire this season, through the lens of BrooksBaseball.net:


One of the reasons many consider Weaver a future reliever is his simple repertoire — one that lacks a consistent third pitch (usually a breaking ball). And as shown in the table, similar to 2013 Michael Wacha, Weaver does indeed rely primarily on a fourseamer-changeup combination. However, the curveball has flashed — in a small sample size, of course — the ability of being an effective third pitch, with solid command down in the zone. It won’t necessarily be a huge swing-and-miss pitch for him, but it will certainly lead to weak, on-the-ground contact. When paired with his propensity to locate his fourseamer up in the zone (see the heat maps below), his “simple” repertoire gains the ability to produce complex sequences.

A noteworthy finding regarding Weaver’s repertoire is the fact that his four pitches are thrown at four separate velocity tunnels. What does this mean exactly? Essentially, if two pitches possess a similar velocity, the same swing by an opposing batter can, in theory, make contact on both. This isn’t the case for Weaver as each pitch varies by at least 4-5 MPH, with an ideal fourseamer-changeup velocity difference of 8.75 MPH. Thus, if he repeats his release point, deception of opposing hitters should come easily. As you can see in the far right column, Weaver has done a pretty good job with his vertical release points. The only critique I’d have is buttoning up the changeup release point, so that it is a little bit closer to that of his fourseamer.

Luke Weaver fourseamer location

Where do you locate when you throw a fast enough fastball, but not one that will blow hitters away regardless of location? The common answer is down, but in actuality, it is considerably more effective to go up. Up and in is especially desirable. Well, Weaver has mastered this approach versus right-handed hitters. And thanks to the great Zach Gifford, we now know that the right-handed league average exit velocity against up-and-in fourseamers thrown by right-handed pitchers is 83.4 MPH. The right-handed league average exit velocity against right-handed fourseamers, independent of zone? 88.9 MPH. For those that still believe down is the way to go, the bottom three zones (91.8 MPH, 92.6 MPH, 89.6 MPH) all carry an average exit velocity greater than the zone-independent average.

While Weaver’s mastered the ability to go up-and-in to righties, he’s so far lived up-and-away to lefties with his fourseamer. Of the three top zones (if unable to visualize MLB’s GameDay zones, click here), up-and-away is the least effective at an average effective velocity of 91.9 MPH. It certainly isn’t the worst location, though, either. Essentially, if Weaver gains the ability to consistently locate the fourseamer inside to lefties as well as he can to righties, the pitch will become even more of a weapon for him. Given the dispersion of the left-handed heat map, it looks as if he is, at the very least, trying to do this on occasion.

What isn’t appreciated in these heat maps is Weaver’s ability to downright paint corners with the fourseamer. Of note, the pitch is technically thrown with a one-seam grip, but for the sake of this article, we will classify it as the more common fourseamer. As usual, I called upon the talents of @cardinalsgifs to help us visualize Weaver’s corner-painting ability.


Strikeout of Carlos Asujae (BrooksBaseball At Bat)

Non-flamethrowing MLB pitchers need a secondary offering in order to retire MLB hitters. While this is generally true in a larger sample, Weaver threw five pitches in his strikeout of Asujae, and all were fourseamers. Despite falling behind 2-0, Weaver came right back with three perfectly-located pitches. As you can see in the back-to-back-to-back trails, all three possessed identical release points despite landing in noticeably different locations. I understand Asujae’s frustration here because even if does make in-play contact, the contact almost certainly wouldn’t be solid.

Strikeout of Wil Myers (BrooksBaseball At Bat)

The ole fourseamer-curveball-fourseamer strikeout sequence. While Myers has been exactly league-average at the plate this season, he’s been above average for his career (108 wRC+). With that in mind, Weaver makes an above-average MLB hitter look helpless in this strikeout. Just like Asujae, Myers is frustrated with the strikes called on the corners because they’re virtually unhittable. I empathize with Mytes because weren’t it for Weaver ability to paint the corners so well this game, these calls could (should?) have gone the other way. It certainly helps having Yadier Molina behind the plate doing the framing.

Oh, and remember my post on Tyler Lyons? In which I discussed his technique of overlapping the flights of his pitches? Well, Weaver follows Lyons’ lead here as his strike two curveball crosses the path of the strike one fastball not once, but twice (if you include the difference in release points).

Strikeout of Manuel Margot (BrooksBaseball At Bat)

Admittedly, I saved Weaver’s best for last, so congratulations to those who are still following along. Pitch sequencing, while complex, is a whole lot of fun. Zach, @cardinalsgifs, and I did our best explaining that back in July. Despite only throwing two of his four pitches, Weaver sequences Margot perfectly, changing his eye level with each offering. After busting him inside with a running 93.7 MPH fourseamer, he dials it up away at 94.9 MPH. In an instructional video on how to attack a right-handed hitter, this strikeout would be a prime example for inclusion.

Bottom line

We do not yet know the longevity of Weaver’s current success. However, with Leake gone, Adam Wainwright injured, and Lance Lynn likely on his way out, he stands as a very important piece for the 2018 Cardinals. Fastball command can take an MLB pitcher a long way. Here’s to hoping Weaver retains this ability while making the necessary adjustments noted above. Weaver might be really good. I am excited to find out because the Cardinals need him to be.

As always, credit to @cardinalsgifs, BrooksBaseball.net, BaseballSavant.com, and FanGraphs for contributions to this post.