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  • Michael Simione

Taking a Look at Pitchers With Large wOBA vs xwOBA Differentials

wOBA vs xwOBA

Below are pitchers with large discrepancies between their wOBA and xwOBA. Before I dive into these pitchers, I should give a quick explanation of what those statistics mean. Weighted on base average (wOBA) accounts for how the batter reaches base. This is different from on base percentage (OBP) which considers only if a player reaches or not. With wOBA, home runs are worth more than triples, triples are worth more than doubles, and so on. Expected weighted on base average (xwOBA) shows what a player’s wOBA should have been based on stat cast data such as exit velocity and launch angle. For a full explanation please click here. Looking at wOBA and xwOBA can help show if a pitcher was getting lucky or unlucky. These can also show how well a pitcher really performed by seeing what kind of hits they gave up; if it was mostly singles instead of extra base hits, wOBA will show us that. The 2019 leaders in xwOBA (min 10 starts) were Tyler Glasnow, Gerrit Cole, Jacob deGrom, and Justin Verlander. Some elite pitchers right there. Now let’s move forward!

The Lucky

Brett Anderson

wOBA .309

xwOBA .343

Difference -.034

Brett Anderson had the worst differential in 2019 as his wOBA was .309 with an xwOBA of .343. Just about every stat shows Anderson was getting very lucky. He finished with an ERA of 3.89 but it came with a 4.60 FIP and 5.29 xFIP. His LOB% was 74.8, slightly above his career average of 70.6, and his BABIP was .278 with a career average of .307. Anderson is a groundball pitcher and his 54.5 GB% was near the top of the league. While that could offset some of these underlying numbers, I wouldn’t bet on him beating out these extreme differences.

Jeff Samardzija

wOBA .290

xwOBA .321

Difference -.031

Samardzija helped out a lot of owners this year providing great draft day value. He finished the year with a 3.52 ERA in 181.1 innings. Just like Anderson, all his underlying numbers show he is due for regression. He finished with a 4.57 FIP and 5.01 xFIP. Had a .240 BABIP (.289 career avg) and a 76.9 LOB% (76.9 career avg). Samardzija threw three pitches - four-seam fastball, slider, and a cutter. His four-seam has a wOBA and xwOBA differential of -0.59 and his cutter had a -0.39 differential. I will be staying away this year.

Luke Weaver

.279 wOBA

.306 xwOBA

Difference -.027

The 2 pitchers directly after Anderson were actually Erick Fedde and Mike Fiers. I decided to skip them though as Weaver here is pretty interesting. While he is towards the top of the list it actually doesn’t worry me. Weaver was breaking out before his injury, and finished the year with a 2.94 ERA in 12 starts. His FIP (3.02) and xFIP (3.61) aren’t bad and would still allow us to expect about a 3.50ish ERA. His BABIP and LOB% are harder to judge since he hasn’t been in the league that long so we can’t determine where those usually run. But Weaver suppressed home runs (0.84 HR/9) and displayed three good pitches in 2019. I’m not worried and still like him as a sleeper.

The Unlucky

Mitch Keller

395 wOBA

.302 xwOBA

Difference + 0.93

I did a deep dive on Mitch Keller which you can read here. He and the next pitcher were by far the unluckiest pitchers in baseball by this metric. Keller finished the year with a 7.13 ERA that came with a 3.19 FIP, 3.47 xFIP, and 3.78 SIERA. Not only that, but he also had a .475 BABIP with a 59.6 LOB%. A lot of people don’t buy into him due to his organization but hey they hired a new staff so you never know!

Blake Snell

.303 wOBA

.264 xwOBA

Difference + 0.39

Mr. Snell was the luckiest pitcher in 2018 and then became the unluckiest in 2019. Snell is still the same pitcher, he has two of the best breaking balls in the game and finished the year with the highest SwStr% among starters (20 start min.). Snell finished with a 4.29 ERA, 3.32 FIP, 3.31 xFIP, and 3.56 SIERA. It looks like I will own a lot of Snell shares this year with his ADP lower than last year (being drafted around the 10th SP on Fantrax).

Carlos Carrasco

.359 wOBA

.325 xwOBA

Difference + 0.34

First, let’s start off by saying thankfully Carrasco is okay and how amazing it is that he will be on the mound in 2020. While there may be a little rust to start next year, I don’t think it will affect him too much. We have to remember Carrasco had four straight years with a sub 4 ERA, and while his 5.29 ERA in 12 starts for the Indians seems worrisome, it did come with a 3.50 xFIP and 3.53 SIERA. He also didn’t lose a step in velocity or SwStr% and seems to be lined up for another good season. All three of his main pitches (slider, four-seam, and changeup) have a positive difference in wOBA and xwOBA. There is nothing here that would cause me to think Carrasco will lose a step in 2020.


wOBA and xwOBA are great stats to add to your research, especially when it comes to gauging if a pitcher is getting lucky or unlucky. I always look at a pitcher’s overall differential and their pitch differentials. As you saw above I then dove into FIP, xFIP, SIERA, LOB%, and BABIP. These are all very telling and can help you evaluate the overall performance of a pitcher. As always thank you for reading and if you have any questions please reach out to me on twitter at @SPStreamer.