The sustainability of Robert Stephenson’s success

Robert Stephenson had a pretty good year out of the Rockies bullpen after coming over from the Reds, posting a 3.13 ERA and 3.63 FIP in 46 innings. His FIP was identical to his very good 2019 season, and his 9.1% walk rate was a career low over a full season. Since the Rockies are always looking for relief help, let’s take some time to go over what made Stephenson successful in 2021 and whether that good performance can see an encore in 2022.

Stephenson throws hard. His four-seamer averaged 96.5 MPH, good for 90th percentile across the Majors, and went close to 100 MPH when he maxed out. Interestingly enough, Stephenson’s fastball has never been a bat-missing pitch despite excellent velocity and spin, even when he played at sea level. In fact, his 16.8% whiff rate on his heater was a career best, which is extremely weird for a pitcher who comes to the Rockies for the first time. His fastball has more run (arm-side movement) than ride (rising effect), which is likely caused by Stephenson’s lower-than-normal arm slot.

Baseball Savant

So, in short, Stephenson’s fastball is a good pitch, with velocity and life, but Coors Field ensures he won’t get all the movement he can out of it. Therefore, my suggestion would be for him to throw it a bit more on the road than at home, and focusing on his two breaking balls in Denver instead. Speaking of which, let’s go over those two.

Stephenson has two different breaking pitches: a mid-80s slider and a low 80s curveball that can sometimes overlap to the naked eye. It’s a situation sort of similar to Germán Márquez, where his slider and curveball have similar velocity and very similar movement. In fact, here’s how similar they are. The chart below represents the average movement of pitches. The oval shapes are Stephenson’s, the ones that look like gears are MLB average. Red is fastball, yellow slider, blue curveball (forget that darker blue, it represents the splitter, which Stephenson uses once in a blue moon):

Baseball Savant

First of all, it’s very impressive that Stephenson manages to have well above-average fastball movement considering the team he plays for (look at that run!), but the two breaking pitches are the focus here. As expected, his curveball doesn’t bite like others, but look at that slider. It doesn’t sweep, but it really drops, and I’d say that it might be his best pitch when considering that he also has a more consistent release point with it. In fact, opponents swung and misses 45.9% of the time when taking a cut at his slider, which is a tremendous number. Therefore, we can only conclude that the Rockies, who are obsessed with the slider, definitely had him use that great pitch a lot, right?

Wrong!

Baseball Savant

Look at that slider usage dropping off a cliff in 2021. You can’t see it, but his curveball became his second-most used pitch at 37.3%, leaving his slider at just 12.5%. That is very unlike Colorado. What happened? Well, Stephenson’s slider got hit early: opponents hit .333 with a homer off of it after using it about 30% of the time in April, and he barely used it in the months after that. Will it tick up again? I’d hope so! Stephenson’s slider has always been his best pitch, and to turn away from it after just a month of bad results seems counterproductive. I’d (hopefully) expect a more even curveball/slider distribution moving forward.

So, what else? We’ve taken a look at Stephenson’s pitch mix, but let’s take a look at the results it produced. Expected stats have limitations, but they’re a good tool for evaluating the quality of contact allowed. Stephenson’s .305 xwOBA (expected weighed-on-base-average) against in 2021 was very good, and while his HR/FB% might have been a bit low (just over 10% when MLB average is around 12-15%), he also didn’t get particularly lucky on batted balls in play, with his .308 BABIP right in line with what you expect out of a Rockies pitcher.

Striking out over a fourth of batters faced is good, and Stephenson did just that (26.4%). We talked about how he posted the best walk rate of his career (9.1%), and if his velocity remains and his release point consistency improves a bit, there’s no reason the righty can’t have very good seasons moving forward, which would go a long way towards stabilizing the bullpen. Of course, relievers are infamously volatile, so you never know.

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Ranking the Rockies’ 10 free agents and their chances of returning in 2022 | The Athletic ($)

I’d say there’s a good chance they try to bring Chacín back as a multi-inning relief arm and personally, something tells me we’re going to see Chris Owings back in a Rockies jersey too.

The Incredible Shrinking Postseason Starter | FanGraphs

From a day or two ago, but man, oh man. 26 postseason games, 52 combined starts, and I’m pretty sure I can count the amount of times a starter has made it to the seventh inning with the fingers of one JPP hand. Good strategy? You can argue it. Good product? Not as far as I’m concerned.

On The Farm

Rafters 2, Javelinas 4

Michael Toglia, Ezequiel Tovar and catcher Willie MacIver were the lone Rockies position players that saw AFL action yesterday, going a combined 0-for-9, although both Tovar and MacIver drew walks, with the backstop scoring one of the Rafters’ two runs on the day. Rockies pitcher Matt Dennis (0.2 IP, 3 H, 2 R, 2 ER, 1 BB, 0 K, 0 HR) got the ball in the fourth inning and couldn’t get out of it, taking the loss after allowing four straight two-out baserunners.

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