Alex Reyes as a Starter: Balancing Ks, BBs, & HRs

Let’s talk about how great Alex Reyes was in 2020.

First, it was exciting that Reyes pitched at all. That’s a feat worth celebrating since it’s something the not-so-young hurler hasn’t done since his debut in 2016. Reyes missed all of 2017. He only managed 4 MLB innings in ’18 and 3 in ’19. Reyes entered summer camp with a positive COVID test and concern that another season could get wiped out. Fortunately, he recovered quickly and gave the club 19.2 innings, the highest total among the club’s right-handed relievers.

Reyes was exceptional despite being asked to cover a variety of roles. He had a 3.20 ERA. He matched that with a 3.24 FIP. He K’ed 12.36 batters per 9 innings. That’s an incredible total, which (believe it or not) only ranked as 4^th on the club last year. He only allowed 1 home run all season. He started a game. He pitched in long relief, often being asked to cover multiple innings. He was Shildt’s choice for postseason closer over the equally incredible Gio Gallegos.

Reyes’ performance has brought a renewal of high expectations from fans and the front office. Once viewed as the top starting pitcher prospect in the game, the Cardinals hoped he would emerge as their future ace and he displayed that kind of upside in 46 innings and 5 starters in 2016. He enters 2021 in a competition for a spot in the starting rotation, though innings considerations will likely limit him to less than a full season of starts.

Let’s start there. How will Reyes’ stats and abilities translate to the rotation? For him, it will all boil down to balance.

What Reyes Does Well: Generate K’s & Weak Contact Through Ridiculous Movement

Reyes’ ability to generate movement on his pitches is truly ridiculous. He throws five-pitch types – 4-seam fastball, sinker, curveball, slider, and a change. In 2020, three of those pitches were among the league leaders in vertical and horizontal movement.

Man, that's tasty. We talk about how great individual pitches are for some players: Adam Wainwright’s incredible curveball, Jack Flaherty’s slider, or Jordan Hicks’ fastball. Reyes has three pitches with that kind of extreme movement in one dynamic arm. The combination of three incredible pitches along with high velocity and more than adequate 4^th and 5^th offerings makes it easy to see why scouts have drooled over him for years and why batters struggle to center him.

One of the things that Reyes has done amazingly well throughout his professional career is to combine extremely high K rates with extremely low levels of hard contact. Consider the following comparison between K/9 and HR/9 at Reyes’ long minor league and major league stops:

Year (Level) - K per 9/HR per 9:
2014 (A) – 11.28/.49
2015 (A+) – 13.57/.00 – no HR’s allowed
2016 (AAA) – 12.81/.83
2016 (MLB) – 10.17/.20
2020 (MLB) – 12.36/.46

When Reyes neared the majors, there was some question about how well his K and HR-allowed rates would hold up. While Reyes does not have enough major league innings to fully answer those questions, the results have remained encouraging. While Reyes’ K rates and HR rates declined during his debut season, he recovered much of that this season. His K and HR stats in 2020 look just like the rest of his pro career.

A-ball hitters were putty in his hands at age 18. MLB’ers were the same at age 26. In 2020, he had one of the lowest expected batting averages in the game at .186. His xwOBA was just .279. Even though his expected slugging percentage allowed was not among the league leaders, his hard-hit % was at 28.9%. His slider and curveball generated high whiff rates – 46.4% and 57.9% respectively. He was not reliant on one pitch to get batters out. He had a “put away %” of 23% or higher on all three pitches, with his slider being the best of the bunch.

While it’s common for a pitcher to experience a significant drop in K rate and a rise in HR rate when moving from the minors to the majors or the bullpen to the rotation, I question how much that will be the case for Reyes. His K’s and contact-rates are not tied to either high velocity or maintaining high spin on one pitch type. In the high minors, Reyes displayed the ability to go deep into games while maintaining both his high velocity and his low HR rates. That was with a slider — arguably his best pitch today — still in development.

It’s also unlikely that Reyes will be expected to go more than 5-6 innings per start in 2021 andl likely won’t receive more than 15-20 starts total as he rebuilds stamina after several years of low innings totals. This type of low-exposure, high-energy approach should maximize Reyes’ skills and minimize concerns that overuse and fatigue could sap his ability to generate K’s and limit damage.

What Reyes Does Poorly: Limit Walks Due to Inconsistent Mechanics & Ridiculous Movement

Walks have always been the bugaboo in Reyes’ otherwise dominant arsenal. Throughout the minor leagues, Reyes carried walk rates that were consistently between 4.00 and 5.50 per 9 innings. Last year, those walk totals jumped to an alarming 6.41.

Why does Reyes allow so many batters? The answer probably lies in inconsistent mechanics, a reality that has plagued Reyes since he was a teenager. I pulled out an old article from VEB’s own A.E. Schafer, which discusses these problems in great detail. I don’t think much has changed in the few years since this was published. Give it a read!

I also believe that the extremely high level of movement that Reyes generates with his pitches contributes to his lack of control.

No one – not the batter, the catcher, or Reyes – really knows where his pitches are going to go. Curveballs that start in the zone can end up in the dirt. Sliders that start on the inner edge can end a foot outside.

When Reyes was younger, many (myself included) speculated that he would have to tame his wildness by cutting down on velocity and movement. The assumption was that his K rate would drop and his HR rate would rise upon reaching the majors; if he didn’t limit BB’s to reasonable levels, he would get shelled.

I no longer believe that’s the case. Yes, walks matter. But K’s – outs with no balls in play – matter more. While Reyes might be able to cut into his spin rate and keep the ball in the zone more often if he slowed down, the sacrifice of spin would likely lead to an increase in hard-hit balls and home runs. Fewer walks and Ks, but more HRs would be bad.

That’s what matters for high walk pitchers. The level of their effectiveness as a starter is tied closely to their ability to generate a high level of K’s AND/OR limit hard contact.

This Fangraphs custom search is my attempt to represent this:

Here we have qualified pitchers from 2015-2019. I eliminated any starter with a BB/9 below 3.5, a ground ball rate above 50%, and a K rate under 8 per 9 innings pitched. This creates a group of starters who are somewhat similar to Reyes in pitching style and expected results.

The first thing you might notice is that no one is a perfect match for Reyes. Robbie Ray is by far the closest, with K rates consistently in the 11-12 range and BB rates in the high 3’s and low 4’s. However, Ray gives up HRs at a rate that is far higher than what Reyes has displayed.

Below Ray, I get wishy-washy about the returns. To match those starters, Reyes would have to see a dramatic drop in K rates. Of course, he would also have to cut his BB rates down. That should reveal how unique Reyes is. Frankly, there are not a lot of pitchers in the game who can generate strikeouts at the rate Reyes is expected to. There are also very few starters who can survive with BB rates as high as Reyes.

Therein lies the balance. To become a productive part of the rotation, Reyes has to be able to find a critical balance between Ks, BBs, and HRs. Here’s how I would like to see that balance play out:

1. Maintain a K rate of 10.5 per 9 or higher while stretching toward 5+ IPs per start. This might be harder than it seems; ZiPS projects Reyes to have a K/9 of just 10.7. Don’t expect Reyes to maintain a K rate over 12 as a starter.

2. Keep his BB totals under 5 per nine. The lower his walk totals go, the better his overall performance will be, but 5 is the breakpoint for viability. ZiPS currently projects him to hold at 4.9 BB/9.

3. Maintain a HR rate at 1.0 or below while pitching deeper into games. ZiPS projects him at exactly 1.0.

I didn’t realize until now just how close my balance points in K’s, BB’s and HRs were to ZiPS actual projections. That helps me feel really good about my analytical instincts. It also allows me to make easy use of ZiPs’ projections to finalize my point.

Szymborski currently projects Reyes to provide a 4.02 ERA and 3.98 FIP in 53 2/3’s innings split between the bullpen and rotation. That’s .9 WAR of overall production.

If we were to throw Reyes back into the chart above and give him a qualifying number of innings (let’s say 165), Reyes would come out with 2.8 fWAR. That fits relatively well. It’s a relatively encouraging WAR/IP total considering Reyes’ career production to this point but not all that exciting in light of Reyes’ insane talent level.

That brings me back to the balance point. BBs, Ks, HRs. If Reyes overperforms in any one of those categories – which is well within his abilities – Reyes’ potential WAR/IP production can climb rapidly. If he underperforms in any one category, he can drop rapidly.

Overall, it seems likely that Reyes can be an average or better starter, even if his rate stats drop from last season. Health might be a greater obstacle for him. Opportunity might be as well, since the Cardinals have several rotation-ready arms. Still, I expect that Reyes’ talent will break all ties and he’ll get at least 15 starts in 2021, with a K rate approaching 11, a .75 HR rate, and BB totals just at 5. The result will be an era at 3.50 in 115 IPs spread over about 15 starts and another 30 relief appearances.

Who wouldn’t take that in 2021?