kWAR and gWAR Season Preview

Five pitchers to watch for from my statistic kWAR/gWAR.

During the summer of last year, Jason Fixelle, the Nationals baseball operations intern, and I worked on a project that we ultimately called kWAR and gWAR. The goal of this statistic was to create a WAR metric that could prove more predictive than fWAR. I won’t get into the details, but if you’re curious you can read a full explanation for the statistic here. 

The first metric, kWAR, is a WAR metric based around the ERA predictor, kwERA, which only accounts for strikeouts and walks. The second metric, gWAR, is a WAR metric based around the ERA predictor GBkwERA which adds ground balls into the kwERA metric. In short, the WAR metrics did end up explaining some of the difference in next year’s WAR value which makes it a useful tool in possibly predicting breakouts or bounce backs.

This is why you are here today reading this article. Here are five players to keep an eye on through the lens of kWAR and gWAR. (It should be noted each player will have a table that has Adjusted values for FIP and ERA, those adjusted values for league not region so they could be misleading. kwERA and GBkwERA were adjusted for the region.)


Blake Snell


The former CY Young award winner has a new home in 2021. From the uneasy dome of the Trop to the sunny skies of San Diego. Much has been made of Blake Snell this off-season with the decision to pull him in game 6 of the World Series and then ultimately being traded a few weeks later. Now let’s figure out how good Blake Snell is, and we’ll take a look at his numbers in 2020. 



While Snell’s FIP seems high, it’s because he had a crazy unsustainable HR/FB% in the small sample season. Because of that, Snell ultimately finished the season with a .6 fWAR but his kWAR was 1.3 and his gWAR was slightly better at 1.4. His SIERA was also around 3.5 which is right in line with his other ERA estimators. All of the estimators saying the same thing is a good sign for Blake Snell. He strikes out hitters at over a 30% clip and gets a groundball rate close to 50% on balls in play. All of that leads to better kWAR and gWAR than fWAR. In this case, we can trust that Snell is closer to his kWAR/gWAR values than his fWAR. 

Snell’s biggest question is how well he will work deep into games, which no metrics can answer. He had problems working deeper into games in 2020 and that’s why Kevin Cash made the decision that he did. In Snell’s defense, he wasn’t going to be given much of an opportunity because that’s not how the Rays operate. He’s got his chance now in San Diego, will his strong estimators help him be able to last deeper into starts is the biggest question for Snell. I would bank on a strong year from the Padres left-hander. 


Chris Paddack 


Sticking in San Diego, Chris Paddack is an enigma to baseball fans and fantasy owners alike. How does a pitcher with good command and strikeout potential struggle so much? Paddack has made headlines since the midway point of the 2019 season about his struggles with his fastball, his inability to keep the ball in the yard, and his poor quality of contact metrics all start to add up. There’s still hope there though. Which, I am sure is coming to either the dismay of fantasy owners who have given up on him or happiness to the fantasy owners who still believe in him even after his 2020.



The results and the peripherals have a large gap. Both his xFIP and SIERA are in line with his kwERA and GBkwERA. Paddack was one of the biggest names to jump out to me when I finished the 2020 data because his kWAR (1.4) and gWAR (1.5) was a whole win higher than his fWAR (.3). It was one of the biggest gaps in all of baseball. It would seem that even if Paddack made no changes, he shouldn’t continue to see the rotten luck that he had been having while in San Diego. 

The good news for Paddack is somehow had shown him that 4-seam fastball had been moving too much like a 2-seam fastball. Paddack admitted he was hesitant on the data but saw the results for himself and has attempted to make a change. Now, all of this data and projection aside, we still need to see the results of Paddack’s fastball. If he can regain his form with that pitch and continue to develop his curveball, he’d easily have one of the better three-pitch mixes in baseball and become the best fifth starter in baseball. 


Aaron Nola


Aaron Nola gets his due from the smart people here at Pitcher List. Prospects 365’s Justin Choi also did a marvelous piece on Nola that you can read here. Nola is one of the very best pitchers in baseball but what if I told you he could get better? Hopefully, you’d believe me because he was better in 2020 than he was in 2019 and put him back closer to his 2018 level. Let’s take a quick look at that 2020 season. 



Nola finished the season with a 2.0 fWAR which was good for 12th in all of baseball. He also had a 2.2 kWAR and 2.4 gWAR. His gWAR value made him tied for 5th in baseball in 2020. I know Nick Pollack has taken some flack for putting Nola 5th in his pitching rankings, but the gWAR statistic might tell you that’s not that crazy. In 2018, Nola was 9th in gWAR. Add onto the fact that Nola had the highest whiff rate of his career and tied for the highest swing percentage of his career, Aaron Nola is a dark horse Cy Young candidate. 

If you’re debating on taking Aaron Nola with your first starter choice in the late first-round or early second round, don’t hesitate. He’s going to be worth it. The groundball rate has been falling for the past few years but it’s still around 50% which is still great for a starter. I can endorse Mr. Pollock’s choice for Nola, and recommend that you draft Nola early, you may regret what he does to your team when you don’t. 


Nathan Eovaldi


Given a large contract after his postseason brilliance, Nathan Eovaldi struggled in 2019 with injuries again. The pressure was on for Eovaldi in 2020 after the injury to Chris Sale, the trade of David Price, and the heartbreaking covid related health issues for Eduardo Rodriguez. He was the lone bright spot for a dismal Boston rotation. The former World Series hero had a strong sample in his 48 innings of work with several indications he could get even better. 



What is so striking about Eovaldi’s GBkwERA is that Eovaldi doesn’t have the reputation of being a ground ball pitcher. Yet, in 2020, he had a 51.5% ground ball rate which was the highest since 2015. Accordingly, his gWAR (1.4) was half a win higher than his fWAR (.9). Outside of getting more balls to be put in play on the ground, he had the lowest walk rate in his career. He set career highs in zone% and first-pitch strike%. Simply put, Eovaldi was challenging hitters and making them beat him rather than beating himself. 

Another thing that shouldn’t go unnoticed is that Eovaldi was missing bats more than ever. He posted a career-high whiff rate this past season which helped lead to his career-high strikeout rate. Now, I know all of this was done in 48 innings of work, but these metrics lead me to believe that he would have gotten better as the season had gone on. With that, there’s always the disclaimer about the health of the Red Sox starter. Factoring that into the decision, I think that Nathan Eovaldi is a potential breakout starter in 2021, who could give a team 130 innings of a 3.00-3.50 ERA this year. 


Matthew Boyd


I know what you’re going to say. There’s no possible way I can convince you to stay on the Matthew Boyd campaign. He’s been a thorn in fantasy owners’ sides for years and after a brief stint of dominance in 2019, it looked like that was all we were going to get out of his potential. He struggled with the home run ball again in 2020 while the strikeout rate fell, and the walk rate rose. Almost everything points to you just ditching ship and letting yourself finally move on. I just want to give you one last thing to consider when we look back at his 2020 performance. 



Now, as you can see, none of those numbers are particularly good. Yet, there’s a big difference between a 6.71 ERA and a 4.48 ERA. A 4.48 ERA is usually around average so why was it 12% worse than the average value? Well, kwERA-, GBkwERA-, kWAR, and gWAR were adjusted for the region in 2020 instead of the league. While a 4.48 kwERA doesn’t look too bad, Boyd’s value was above that of the central region which saw a lot of dominant pitching. However, he still had a .9 kWAR and .8 gWAR. Those are the same values as Adam Wainwright in similar innings. Maybe there’s still average pitcher potential. 

I know, I know, I know, we’ve done this dance a million times. The other baseline numbers may not support that, but Boyd wasn’t getting ahead of hitters at the rate he was in 2019. If he can rediscover his command, then maybe there is hope for him yet. His whiff rate was still the second-highest rate of his career. Am I just grasping at straws? Maybe! Perhaps it’s time to move on from Matthew Boyd, but if you just need a pitcher to eat innings and are in the later rounds, there are worse options to have. 

Photos by Gregory Fisher, Brian Rothmuller, Frank Jansky, Cliff Welch /Icon Sportswire | Design by Quincey Dong (@threerundong on Twitter)

Max Greenfield

Former Intern for the Washington Nationals, now a Going Deep Writer analyzing the next possible breakout pitcher.

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