Corbin Burnes’ early season performance is transcending belief, but he’s not going away any time soon.
In this article, we will explore how Burnes got here by diving deep into the year-to-year progression that made him into the ace he is today, starting with his debut season in 2018.
2018 (38.1 IP): 7-0, 2.61 ERA, 3.46 SIERA, 1.00 WHIP, 8.3 K/9
Burnes was pretty much exclusively a four-seamer/slider pitcher at this point, though he mixed in a curveball just over six percent of the time. Pitching out of the bullpen allowed him to succeed with a two-pitch repertoire, as both the fastball and slider kept hitters in check for the most part. Burnes wasn’t dominant in any one statistical category, but he was well above average in terms of hits allowed and slightly better than average in strikeouts, walks allowed, and home runs allowed. It’s rare to see a rookie pitcher put together such a well-rounded season, so how did he do it?
Burnes’ four-seam fastball averaged 95.2 MPH and allowed just a .174 BA (.243 xBA), .244 SLG (.375 xSLG), and 88.4 MPH average exit velocity, but it did produce a fairly poor 22.1% whiff rate. The pitch was very hittable but Burnes managed to generate a lot of weak contact with it because he consistently commanded it well in the bottom quadrant of the zone. The movement profile and velocity don’t jump off the page, but a 95 MPH fastball, if commanded well, can still be effective.
Burnes’ slider was his best out pitch in 2018 and it was above average compared to others around the league. The slider averaged 86.6 MPH and allowed a .209 BA (.204 xBA), .465 SLG (.393 xSLG), and 89.9 MPH average exit velocity to go along with an excellent 47.6% whiff rate. The pitch underperformed according to Statcast and was hit hard at times, but the whiff rate was its saving grace. In fact, 18 of Burnes’ 35 K’s came on sliders despite the fact that he threw the pitch only 34.2% of the time. The pitch’s vertical and horizontal movement was better than average even though he threw the slider fairly hard at almost 87 MPH. That nasty movement profile combined with Burnes’ ability to locate the slider both down and away to righties and low and inside to lefties is what made it an asset in 2018.
Burnes’ curveball was disastrous and not even worth talking about, so let’s put a bow on Burnes’ 2018 season. Burnes clearly overperformed according to SIERA, but even the 3.46 SIERA is nothing to sneeze at for a rookie. While he did do everything fairly well, the strikeout numbers lagged behind the better relievers in the game, and his stuff overperformed a bit relative to expected stats. At this point, Burnes didn’t have a viable third pitch and he was only a rookie, so there appeared to be plenty of growing left for him to do.
2019 (49.0 IP): 1-5, 8.82 ERA, 3.55 SIERA, 1.84 WHIP, 12.9 K/9
When it comes to Burnes’ 2019 implosion words just can’t do it justice. The Brewers tried him out as a starter, but he only made four starts due to his struggles. The astronomical ERA/WHIP jump out — but look at the SIERA. Burnes’ 3.55 SIERA is just .09 higher than his 2018 mark, while his ERA increased by 6.21. Let’s take a look at some of Burnes’ per nine-inning figures in 2019 vs 2018 to give some context to his inflated ERA and WHIP.
Burnes added a changeup to his pitch mix in 2019, but only threw it about four percent of the time while his curveball was only used around seven percent of the time, so he was primarily a four-seam fastball (52.5% usage) and slider (31.1% usage) pitcher once again. So, if it wasn’t a pitch mix change that caused Burnes to implode despite the increased punchouts, what was it exactly? Simply put, Burnes’ fastball went from asset to liability and he had really bad luck. In order to fully understand how Burnes progressed/regressed in 2019, we should examine how his arsenal developed in addition to analyzing his bad luck from a macro perspective.
First, let’s take a look at what went wrong with Burnes’ fastball in 2019. The fastball was so bad that it completely negated improvements he made with his slider. Simply put, he didn’t add movement/velocity and he totally lost his command of the pitch. Burnes pulled off something rare in 2018 when he successfully threw a non-sinking fastball low in the zone with regularity, but he was unable to replicate that success in 2019 when he left the pitch middle-up in the zone far too often. On the year the pitch allowed hitters a whopping .425 BA (.344 x BA), .823 SLG (.659 xSLG), and 91.8 MPH average exit velocity without getting many whiffs (19.7 whiff%). You can see that Burnes’ expected stats with the fastball were far better than the actual numbers, but even the expected stats show that the pitch was flat out terrible in 2019. If you’re not getting whiffs and not generating soft contact this is what happens.
On the bright side, Burnes’ slider truly became one of the nastier pitches in the game in 2019. Corbin increased his average slider velocity to 87.9 MPH, maintained good vertical movement, added 1.2 inches of horizontal break on the pitch, and commanded it consistently outside of the strike zone. That combination led to the pitch generating an awesome 57 percent whiff rate, which was the second-best slider whiff rate in the league among starting pitchers. In addition to the 57 percent whiff rate, the slider allowed opposing hitters the following minuscule numbers: .181 BA (.170 xBA), .306 SLG (.274 xSLG), and 87.4 average exit velocity. Those marks are nothing short of stellar; not only did Burnes’ slider limit loud contact, it rarely allowed it at all. Unfortunately, he only threw the pitch 34.2% of the time because he couldn’t consistently locate it in the zone for strikes. Despite that fact, he may have been better off bumping the slider usage to 40%+ and walking more guys than he was throwing his other pitches. The improved slider was pretty much the entire reason why Burnes’ K/9 jumped so drastically, and it gave him something to hang his hat on during the nightmare 2019 season.
Now let’s look at just how ridiculously bad Burnes’ luck was in 2019. Here is a table that compares Burnes’ 2019 metrics against league averages in three key peripheral statistics that pitchers have little control over.
|Statistic||Historical League Average||Corbin Burnes 2019|
|Batting Average on Balls In-Play||.300||.414|
|Home Run to Fly Ball Ratio||10%||38.6%|
|Left on Base Percentage||70%||57.4%|
The unfortunate discrepancies between Burnes’ 2019 stats in these categories and the historical league averages are staggering. Burnes was clearly a victim of uncontrollable misfortune much of the time, which explains his 3.55 SIERA being so much lower than his 8.82 ERA.
2020 (59.2 IP): 4-1, 2.11 ERA, 3.18 SIERA, 1.02 WHIP, 12.3 K/9
The 2020 season was a massive one for Corbin Burnes’ career, and the improvements and changes he made in that time are a big reason why he’s currently vying for the title of MLB’s next ace. 2020 was also the first year that Burnes became a true starting pitcher, though the Brewers were still cautious with his innings and pitch counts, which resulted in a small number of relief outings. Looking at the numbers, you can see that Burnes posted a career-best ERA while maintaining an excellent WHIP and strikeout rate — let’s explore why.
The first factor is that Burnes simply experienced some good luck for a change, as his LOB%, BABIP, and HR/FB % all came in better than league average. Burnes needed his atrocious luck to change, but the main reason for his emergence was a completely reworked repertoire. Burnes’ two primary pitches in 2020 became a sinker (33.1% usage) and a cutter (31.5% usage), two pitches he threw just 3.7% and 0.9% of the time respectively in 2019. He also toned down slider usage to just 12.7% while finally adding a legit changeup (11.2% usage) and curveball (9.1% usage). Let’s break down Burnes’ altered pitch mix to get a better idea of how Burnes resurrected his career and put himself on the path to stardom.
Burnes’ sinker was his primary pitch in 2020 after being a complete afterthought in prior years, and it was one of the hardest sinkers thrown by any starter at 96 MPH. While the pitch didn’t get a ton of movement, it still moved a lot more than Burnes’ very poor four-seamer that he utilized in 2019. The added movement and velocity that came with the change to the sinker gave Burnes a fastball that was essentially a net neutral pitch instead of a liability. Here’s how opposing hitters faired against the sinker in 2020: .250 BA (.315 xBA), .406 SLG (.581 xSLG), and 91.6 average exit velocity. The exit velocity and expected stats tell you that Burnes’ sinker was still not a good pitch, and it likely overperformed its true value in 2020. Nonetheless, it set up his other offerings and was only thrown 33.1% of the time, so it didn’t hurt him as bad as the straight four-seamer did in 2019 when he threw it a massive 52.5% of the time. The pitch’s whiff rate (18.4%) was also not ideal compared to all pitches league-wide, but it was better than the average sinker for what it’s worth.
This is where things start to get really fun! Burnes introducing a cutter in 2020 could be the most important thing he ever did for his career. Right away it became clear that Burnes’ cutter was a dominant offering. Thrown with good average velocity (93.1 MPH) and wicked horizontal movement, the cutter overmatched hitters all season long. Burnes did a great job locating the pitch down and away to righties and down and inside to lefties, but its movement profile also allowed him to use it up in the zone for whiffs when he needed to. When Burnes did make mistakes with the cutter its electric movement/velocity often allowed him to get away with it. All told, hitters posted the following very poor statistics against the pitch in 2020: .162 BA (.169 xBA), .203 SLG (.285 xSLG), and 84.6 MPH average exit velocity. Burnes’ cutter also held the best whiff rate (32.9%) and second-best hard-hit rate (23.7%) of any cutter thrown by a starting pitcher in 2020. By Statcast’s pitch run values metric Burnes’ cutter was easily the most valuable cutter in baseball during the 2020 season. It’s incredible that a pitch Burnes threw less than one percent of the time in 2019 turned into the best cutter in the league the very next year, but it speaks to his work ethic and supreme talent.
Burnes’ cutter was the biggest factor in his resurgence, but we should also look at the off-speed pitches that contributed to his dynamite five-pitch mix. The slider was even more ridiculous in 2020 than it was in 2019. Burnes subtracted a bit of velocity while adding more horizontal movement and it resulted in very little hard contact and an insane 60.3% whiff rate that was second-best among all qualified pitchers (minimum 25 PA). As for the revamped changeup, it was thrown 11.2% of the time, typically below the zone, and it allowed opposing hitters just a .182 or worse BA, xBA, SLG, and xSLG — talk about dominant. The changeup was thrown hard at almost 89 MPH on average and it didn’t have a ton of movement, but it tunneled beautifully with his sinker and hitters couldn’t tell the difference until it was too late. Lastly, let’s talk about the much-maligned curveball. After having a lot of trouble with his curveball in years past Burnes excelled with it in 2020. The difference wasn’t in velocity or movement but in location. Burnes located the pitch down in the zone and didn’t hang it nearly as much as he had in past seasons. With better command, the pitch was virtually untouchable, as it racked up a 47.1% whiff rate and hitters batted and slugged just .095 against it on the season.
It became clear after 2020 that Burnes could be special. In just one off-season he managed to successfully evolve the usage and performance of just about every pitch in his arsenal. Going into 2021 Burnes had already created a true ace-like foundation for himself by improving exponentially over the prior year, and he didn’t stop there.
2021 (12.1 IP): 0-1, 0.73 ERA, 1.04 SIERA , 0.16 WHIP, 14.6 K/9
It may not be possible for Burnes to make the type of jump he made from 2019 to 2020 ever again, but it sure looks like he’s determined to finish better than sixth in Cy Young voting in 2021. His numbers to date are hard to believe, but if you’ve watched him pitch in his first two starts you would know that they are well deserved. It’s still too early to determine stable usage rates on pitches, but unfortunately for hitters, it looks like Burnes is trying to further optimize the usage of his best pitches while fazing out a bad one. In two starts Burnes’ pitch usage looks like this: cutter (50.0%), changeup (14.2%), sinker (12.6%), curveball (11.8%), slider (9.8%), and four-seamer (1.6%). Burnes seems to have honed his command of the electric cutter enough that he can throw it more while scaling back the usage of his poor sinker. If that wasn’t enough, Burnes has also added between 0.3-3.0 MPH of velocity to every one of his pitches and further optimized each offering’s movement profile, save for the sinker. To wrap things up, I want to look at where Burnes is with each pitch right now before providing some big picture analysis.
The cutter that turned Burnes’ career around went from being a great pitch in 2020 to being a nearly untouchable offering so far in 2021. Somehow Burnes is throwing his cutter a full three ticks harder than he did last year, averaging 96 MPH with the pitch. Going back to 2017, the first year Statcast’s pitch arsenal leaderboard data existed, no pitcher in baseball, starter or reliever, has ever thrown a cutter that hard. What’s even more remarkable is that Burnes is still throwing it with nasty movement at that ridiculous speed. Almost understandably, hitters are batting a pathetic .067 with a .167 SLG against the cutter early on despite Burnes throwing it in the zone with regularity.
As for the off-speed pitches, so long as Burnes follows his 2020 blueprint with the slider/changeup/curveball (locate down below the zone in whiff counts) they should dominate hitters once again. I say that because he’s added phenomenal movement to each of those pitches, and they were already nasty last year. The off-speed stuff is great, but amongst Burnes’ non-cutter offerings, it’s the sinker that I’m most interested in watching the rest of the way. Specifically, I’m interested in its usage and its movement profile. In 2020 Burnes’ sinker was really his only pitch that hitters barreled up consistently. Burnes did add a tick of velocity to the pitch that might help its performance, but its movement profile hasn’t improved thus far and it’s once again been the only pitch that opposing hitters have been able to do damage with early in the year. I’d love to see Burnes continue throwing it around 12.6% of the time as he has so far, that way it can be utilized situationally instead of regularly. Maybe there’s a hitter that hits cutters and off-speed pitches fairly well but struggles with straighter velocity, or maybe Burnes badly needs a double play and he doesn’t have a good feel for his offspeed pitches that day — those are the types of instances when the sinker should be used. The bottom line is that if Burnes is to fulfill his promise this season and beyond he cannot throw his fringy sinker more than 20 percent of the time; the other pitches are all way too good to be wasted.
Hitters won’t have a chance against Burnes going forward if he can keep his command sharp, continue to sprinkle in his nasty secondaries, and maintain most of the early gains/increased usage he’s showed with the cutter. If Burnes does those things consistently he will be a perennial 2.80-3.30 ERA pitcher to go along with 200+ K’s and a WHIP near 1.00, or in other words, an ace. Going forward, concerns could arise with Burnes if he overuses the sinker, loses velocity/movement on his stuff, or loses command of his arsenal, but none of those things seem remotely likely at this point in time. True aces are so rare that we oftentimes crown pitchers too early, or even overlook them before they reach their potential, but make no mistake this time— Corbin Burnes is Major League Baseball’s newest ace, and he’s here to stay.