Pitch tunneling with Luke Weaver

Considering the front office's confidence with internal pitching options as the regular season draws near, the importance of Luke Weaver pitching well in 2018 simply cannot be understated. After a rocky big-league debut in 2016 (5.70 ERA over 36.1 innings pitched), Weaver was stellar upon MLB promotion last year and projects reasonably well (2.1 zWAR and WARP) for 2018 in (notoriously conservative) projection systems like ZiPS and PECOTA. While Weaver was a quick riser through the system -- after being drafted 27th overall in 2014 -- he was never really considered a top prospect, nationally, along the way. In fact, most scouts pegged him as a future reliever, citing concerns with his mechanics and his lacking of a true third pitch.

Well, depending on whether or not you believe in Michael Wacha (for what it's worth, I do, and I explained why last week for Baseball Prospectus), Weaver is slated as either the number two or number three starter to open 2018. For a pitcher with a grand total of 96.2 MLB innings, on paper, this feels like a bit of a stretch. Fortunately, Weaver's repertoire and approach to tunneling help provide a solid foundation for continued MLB success.

At the Winter Warmup, I asked Weaver a poorly-worded question about the launch angle versus his up-in-the-zone fastballs. His response, "I am going to sit here and pretend like I know what you're talking about." Essentially, I was trying to praise him for being successful at combating the "fly-ball revolution," as his high heat held hitters to an average launch angle of 16.1 degrees, as compared to a league average of 21.1 degrees. This allows for continuity with his new pitching coach, Mike Maddux, who has been stressing the importance of the high fastball all spring.

And when you look closer at Weaver's 2017 repertoire, via BrooksBaseball, the reasoning behind this approach becomes clear:

As primarily a fastball-changeup pitcher (85.92 percent combined), going up with the fastball and down with the changeup makes so much sense, given the ability to locate each pitch, of course. While walk rate is more indicative of control than command, Weaver's career walk rate (hovering around 7 percent) shows a baseline for being able to roughly locate each of his top two pitches.

However, Weaver cannot exclusively throw fastballs up, changeups down and expect to remain successful forever. MLB hitters adapt very quickly, particularly with the amount of information made available via video and scouting reports. Thus, please don't misconstrue what is written above as Weaver being nothing more than a one-dimensional pitcher, especially when you consider the positive steps he has taken with his curveball (I will more on this pitch later).

That being said, it certainly helps to be really good at that one dimension. If Baseball Prospectus' new pitch tunneling metrics -- available in BP's stats section -- are any indication, Weaver is among the league leaders at tunneling the fastball-changeup and changeup-fastball sequences. Before getting into the data, I recommend reading my Pitch Tunneling 101 post if you have not already. I discussed pitch tunneling in podcast form as well. So, "among the league leaders," you ask? What exactly do I mean by that?

In my opinion, the most informative tunneling metric, at this stage at least, is PreMax (measured in inches) -- which is short for Pre-Tunnel Maximum Distance. In other words, PreMax represents the “distance between back-to-back pitches at the decision-making point.” In the most simplest terms, the smaller the PreMax the better. A smaller PreMax means the pitches are closer together at the point in which a batter must determine whether to swing or not.

In 2017, Weaver's fastball-changeup PreMax versus righties was 1.35 inches. Only 13 pitchers exhibited a smaller fastball-changeup PreMax last season, notables including Chris Sale (1.34 inches versus righties) and Luis Castillo (1.31 inches versus righties and 1.32 inches versus lefties). While Weaver was slightly worse at tunneling fastball-changeup versus lefties, a PreMax of 1.48 is still slightly better than league average. And when you reverse the sequence to changeup-fastball, Weaver's solid PreMax values continued as he yielded 1.31 inches versus righties (top 25) and 1.43 versus lefties (top half). To better visualize just what these numbers mean, I called upon the talents of @cardinalsgifs, and as always, he delivered.

But first, a necessary disclaimer: One thing I have learned during my tunneling research is that while the center-field camera is ideal for an appreciation of overall pitch movement (and a representation of the strike zone), it is not the best for visualizing pitch tunneling. Remember, pitch tunneling is focused on what the batter sees from his stance in the batter's box, and not what we see on the TV broadcast. Thanks to extraordinary advancements over at Baseball Prospectus, we now have the Batter v Pitcher Matchup Tool, giving us a better look at what the batter sees.

The fastball-changeup sequence

Versus Neil Walker, on August 29, 2017

And from Walker's point of view, via Baseball Prospectus:

The changeup-fastball sequence

Versus Domingo Santana, also on August 29, 2017:

And, my personal favorite, the stereoscopic version:

And utilizing the Baseball Prospectus matchup tool:

Versus Marcell Ozuna, on July 5, 2017:

And the BP version:

The curveball

This is such an important pitch for Weaver going forward. In Weaver's own words, via Benjamin Hochman:

“It’s been a big pitch for me. The change-up has kind of always been that pitch to go to. But to separate me, I needed that next pitch. … Because in bullpens it’s always been good, but the game speed, when things are ramping up, the pressure’s on, it’s — how can I execute? And I finally found that curveball, to where I can consistently throw it, same slot, get that good spin, just throw with confidence."

While the changeup and cutter are thrown slower than the fastball, over time, a third -- even more distinguishably different -- velocity window is necessary. The curveball provides that window for Weaver, as it averaged 79.83 MPH last season. And with the pitching staff's focus on high fastballs under Maddux, Weaver's curveball will still be able to tunnel reasonably well with the fastball. I use the qualifier "reasonably" because curveball typically don't tunnel well with other pitches. Look no further than this September 14th at bat for a nearly perfect fastball-curveball tunnel.

Versus Tucker Barnhart:

Remember my disclaimer from earlier? Given the angle of the TV broadcast, these two pitches don't appear to tunnel well at all. However, now that we have Baseball Prospectus' new matchup tool, we can better understand just how difficult of a two-pitch sequence this was for Barnhart to maneuver:

Bottom line

Weaver enters 2018 with a spot solidified in the starting rotation. Though he still has not yet reached the century mark in MLB innings, it isn't difficult to possess confidence in the 24-year-old, especially considering his repertoire and approach appears to gel with his new pitching coach. I expect a strong season from Weaver in 2018. The Cardinals need one, at least.

As always, credit to @cardinalsgifs, Baseball Prospectus, BrooksBaseball, Baseball-Savant, and FanGraphs for their respective contributions to this post.