Drew Rasmussen has not reached his final form

The Rays believe Rasmussen is a starter, but he may need to make some changes to his arsenal

Before the Rays acquired Drew Rasmussen and J.P. Feyereisen, both pitchers were filling similar, middle relief roles for the Milwaukee Brewers — the two were even catch partners at one point.

Once coming over to Tampa Bay, both saw their roles change. Feyereisen immediately joined The Stable, while Rasmussen was slowly but surely stretched into being a full time starter while working with an extra day’s rest, with his last eight games being traditional starts which lasted at least four innings.

All told, Rasmussen pitched to a stellar 2.84 ERA and 3.09 FIP in 59 innings. During his time as a starter, he was even better, pitching to a pristine 1.46 ERA and 2.76 FIP.

In 2022, it’s safe to say the Rays expect big things from Rasmussen. As of now, he slots as the No. 2 pitcher in the rotation after Shane McClanahan, and while that may not be how things shake out on Opening Day, it’s more than reasonable to think that Rasmussen deserves to be in that slot, even ahead of tenured starters like Ryan Yarbrough (if he’s not traded) or the newly acquired veteran Corey Kluber.

But as great as Rasmussen was on the surface, that of course does not mean the he doesn’t have a bit of work to do. While Rasmussen possesses a plus-plus fastball that averages over 97 mph, he is mostly a two-pitch pitcher, and his main secondary offering, the slider, leaves a little to be desired.

Rasmussen did well to prevent runs during his time with the Rays, but he didn’t miss a ton of bats, striking out just 20.9 percent of batters. This of course isn’t to say that pitchers need to miss bats to be good, but to be fair, that is what Rasmussen’s skillset is designed to do. And just as Rasmussen was a moving target in 2021, who we will be in 2022 is sure to be as well.

Let’s start with a few adjustments that have already happened.

As per usual, the Rays waste no time tinkering with pitchers once they acquire them, nor are they shy about tinkering with pitchers who have tenure. Both of these are true about Rasmussen, as some changes were immediate, while some were more gradual.

Level 1: getting extended

Unlike Feyereisen, who stepped into a high leverage relief role immediately upon joining the Rays, Rasmussen was assigned to Triple-A. One thing that changed right away from his time with the Brewers to his time with the Rays was his release extension.

While it is far less drastic than the shape of the graph might suggest, it seems that the Rays worked with Rasmussen to add release extension while he was down in Durham. For a pitcher like Rasmussen, who already possesses elite velocity, the extra extension makes his fastball play even faster than it already is. This is known as perceived velocity.

As a Ray, Rasmussen averaged 97 mph on his four-seam fastball, but clocked 97.52 mph on average in perceived velocity. Thanks to his greater extension, the pitch played just over a half a mile an hour faster just by him reaching out a little farther. In today’s age of baseball, terms like extension and perceived velocity seem somewhat dated, as they have been around even longer than things like spin rate or launch angle.

The Rays, however, seem to be bought into this with renewed vigor, as they had the second highest average release extension as a pitching staff in 2021. So while Rasmussen’s release extension was well above the league average, it was brought up to around the average for the team. With that said, he was one of the better performers when it came to perceived velocity beyond actual velocity. As an added bonus, note the correlation between release extension and this particular metric.

For fun, I’ve also highlighted two pitchers recently traded away from the Rays.

Level 2: fixing the slider

The slider is an important pitch for Rasmussen, as it is his go to secondary pitch, going to it roughly 30 percent of the time. at 2655 revolutions per minute, that ranks in the 89th percentile. This is important because as we now know post sticky substance ban, spin rate is not something that can be learned, and if a pitcher has it, they should take advantage of it.

It is important to say here that Rasmussen’s slider is not a bad pitch as it is now. After all, his fastball-slider combo is what got him here. But at a sub 30 percent whiff rate, it is not the wipeout power slider one would expect from a profile like Rasmussen’s. That might change come 2022, as he started to add more horizontal movement to the pitch toward the end of this season.

As Cole Mitchem already pointed out, this is something the Rays may be targeting when looking to acquire pitching, and it is clear that they thought this could work for Rasmussen. For 2022, this could be more apparent, since Rasmussen can spin the baseball better than most pitchers.

For a visual, here are two sliders from Rasmussen placed side by side. Notice how the pitch on the left from his time with Milwaukee is more of an up and down pitch, while the one on the right with the Rays has better two plane movement.

The difference here is 0.34 inches to 5.37 inches of horizontal movement, respectively. In other words, he’s no longer throwing a cement mixer. If Rasmussen is going to mostly be a two pitch pitcher, the slider is going to need that two plane depth in order for him to work as a starter.

The Rays already tinkered with the shape of Luis Patiño’s slider, changing it from a pitch that was much more vertical in 2020 to a pitch that resembles a slider-cutter hybrid. While the Rays may not quite go that route with Rasmussen, there could be more where that came from next year.

Had the season progressed beyond October, it’s easy to imagine we would have continued to see progress on Rasmussen’s secondary offering. The Rays have been connected to Rasmussen long before his acquisition, so surely these plans have been in the works for quite some. What can we expect next?

Now that we have talked about the adjustments Rasmussen has already made to be better in 2021, in my next article, we will discuss some future changes he might make to unlock his full potential as a starter for the Rays in 2022.