The goal of this post will be to show why I believe Tanner Rainey is underperforming, and how even though he has a similar movement profile to Nick Anderson, that does not mean they have the same Vertical Approach Angle (VAA).
To start, here are their comparable movement profiles from Brooks Baseball.
The few red plots for Rainey above the 0" Vertical Movement line are from 2018, he added depth to his slider in 2019. These two players are great examples of how movement profiles are way more important than the actual name of a pitch. Baseball Savant lists Anderson's breaking ball as a curveball, whereas Brooks Baseball classifies them as sliders. I will refer to both players' secondary pitches as sliders in this post.
2019 averages, according to Baseball Savant and Baseball-Reference:
Rainey ERA/FIP: 3.91/4.37
Anderson ERA/FIP: 3.32/2.35
Rainey FB xwOBA: .406
Anderson FB xwOBA: .310
Rainey FB whiff %: 30%
Anderson FB whiff %: 30%
Rainey FB velo: 97.7 mph
Anderson FB velo: 96 mph
Rainey FB vertical movement: 10.9"
Anderson FB vertical movement: 10.3"
(*I should have made note in previous posts, but Baseball Savant uses data that is different than your Rapsodo/Trackman data. The lower the vertical movement is on a fastball, the more carry it has which is counterintuitive to what Rapsodo/Trackman tell us. The greater the vertical movement number on Baseball Savant, the more "drop" a pitch has.)
Rainey FB horizontal movement: 4.1"
Anderson FB horizontal movement: 5.8"
Those are pretty similar fastballs as far as velocity and movement goes, especially vertically. Now here are their VAA heat maps.
The first thing that probably stands out is the coloring and how much more Anderson elevates his fastball than Rainey, which is important and I will circle back to. But check out how their average VAA is about a degree different moving up and down zones, regardless of having such similar movement. This is due to their release height differences (Rainey 6.2 ft, Anderson 6.6 ft). In this post, I wrote about how fastballs generally perform better the closer the VAA is to zero. So not only is Rainey not elevating his fastball enough to the zones that produce better results, but I actually believe he would have better results than Anderson up in the zone due to the flatter VAA. Not to mention, Rainey averages almost 2 mph more on his fastball.
I thought it was interesting that both pitchers' fastballs had a 30% whiff rate. This leads me to believe that Rainey's rate would increase even more than Anderson's because if he can get 30% whiffs by throwing to the "non-optimal" zone, it should improve when throwing to the "optimal" zone.
Both pitchers are two-pitch pitchers, as well. Anderson throws his fastball 60% of the time, where Rainey throws it 71% of the time. Despite a .149 xwOBA and 63% whiff rate on his slider, Rainey throws it just 29% of the time. Anderson's curveball/slider has an xwOBA of .173 and whiff rate of 54%.
So why doesn't Rainey elevate more with the fastball and throw it less to take advantage of an above average slider? Nearly every fastball video I watched had Rainey's catcher setting up low and away, so it's not that I don't think he can't locate up, I just don't know that he tries to do so enough. One reason his slider may be so effective is because he throws his fastball low and away, allowing him to tunnel the slider off of the fastball. I am not saying Rainey should never throw there, just that he should try to elevate more and throw the slider more. He seems to locate the slider better than Anderson, as well, judging by this heat map below.
Compared to Anderson...
Recap
My original point was to show how I believe Tanner Rainey could not only improve his current performance, but how he can be better than a comparable pitcher in Nick Anderson. Maybe I got a little sidetracked with all of the reasons why, but another main point of this post was to demonstrate how comparable movement profiles have different vertical approach angles, and should not be evaluated solely on vertical and horizontal movement.
So to reiterate, I think Rainey would perform better by 1) elevating his fastball more, and 2) throwing his slider more.
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