2023 Review: Hitter wOBA vs xwOBA

Let’s start reviewing 2023 performance. We’ll start with hitter wOBA, comparing it to Statcast’s xwOBA. Why should we care how a hitter’s actual wOBA compared to his xwOBA? Because if you’re reading this, you’re probably a fantasy baseball player, and if you’re a fantasy baseball player, you probably want to either get your hands on a good set of projections or forecast players yourself.

Identifying the hitters who both underperformed and overperformed their xwOBA marks might help you recognize hitter projections that might be too optimistic or pessimistic, if your source isn’t incorporating Statcast data. If you’re manually projecting players yourself, you might want to weigh the player’s actual performance less heavily, and rely more on how that hitter was expected to perform given the underlying drivers of the xwOBA calculation.

Before diving in, it’s important to remember that no equation is perfect. There will always both be outliers based on randomness or player skills that are difficult or even impossible to quantify that would help explain any disparity between wOBA and xwOBA. Therefore, it also helps to review a hitter’s wOBA-xwOBA difference history to identify any patterns. With those caveats out of the way, let’s begin by reviewing the hitters that underperformed their xwOBA marks the most. I also added Steamer’s 2024 xwOBA projection, as that’s the only one currently available.

Well gosh darn! The hope when identifying underperformers is highlighting players who may be undervalued or be considered a “sleeper” in fantasy leagues. Unfortunately, four of the six names here are absolute superstars! Perhaps a future article will only include players drafted outside the top 100 or something.

It’s quite comical to find Aaron Judge’s name at the top of the xwOBA underperformers list, and it’s not even close. He’s the only one who underperformed by more than .040 points! What’s totally crazy is that he actually posted a slightly higher xwOBA than his 2022 mark when he hit 62 home runs. While his xBA was slightly lower this past season, his xSLG was actually higher, which is just nuts! If you could believe it, he just posted a 27.5% Barrel%, versus an 8.1% league average. That’s not only a career best, but the highest mark by a hitter with at least 450 PAs in a season since Statcast has existed. I’m sure you could guess who ranks second and third — that’s right, Judge as well!

While everything sounds rosy, do be aware that his strikeout rate and SwStk% jumped in 2023, while his FB% surged to a career high 50%. He had never posted a FB% higher than his 2022 mark of 43.5%, so regression there could reduce his HR/AB rate. Oh, and obviously injuries have been an issue and now heading into his age 32 season, it’s unlikely that risk is going to go away.

Hooray for Michael Massey’s name appearing second here, because he’s precisely the type of player I had hoped would make this list. With an expected full-time job heading into the season, Massey was somewhat of a sleeper with both power and speed contribution potential. While he did kind of deliver, he was still pretty disappointing and ended up losing at-bats, though probably not as much as you might have expected. Massey still figures to be the team’s second baseman this year, though on the strong side of a platoon as he hits from the left side.

The good news is that Statcast suggests he was quite unlucky last year, both seeing fewer hits drop than expected thanks to his .261 BABIP, and hitting for less power as well. With a strong LD%, it’s quite surprising that he finished with such a low BABIP, though a lot of that line drive rate is offset by a big 45% FB%. If there ever was a hitter that shouldn’t be hitting so many fly balls, it’s Massey. Seriously, why is a guy with league average power hitting so many flies?! The liners are great, but this is a weird batted ball profile that doesn’t fit Massey’s skills. That said, if his luck reverses, perhaps he won’t completely lose his job, and he might even convince the team to start him against lefties. He’s therefore not a bad cheap speculation in deep leagues.

Joc Pederson’s appearance here represents another non-superstar name that could could result in actionable advice. Currently a free agent, his ultimate value will depend heavily on the team he signs with and his expected role. He’s been a strong side platooner for his career, and after a decent enough .331 wOBA, you would expect that role won’t change. But this is now two seasons in a row where he posted an almost identical wOBA, both of which set new career highs. You have to imagine that going anywhere from San Francisco is going to be good for his offense.

Pederson has shown a lot of promising skills and positive trends. His walk rate jumped to the second highest of his career, while his strikeout rate dropped to its best since 2018. His maxEV shot up to a career high, while his Barrel% matched the second highest mark of his career. Yet, his HR/FB rate slipped to the lowest mark of his career, as did his ISO. I love when the Statcast metrics don’t match the results, as the results could be influenced by more outside factors, suggesting there’s serious rebound potential here. He probably still won’t have any shallow mixed league appeal, but could be a deep league bargain, especially in leagues that use OBP instead of batting average.

Fernando Tatis Jr. is a good example of what could happen to a hitter’s power after returning from shoulder surgery. His HR/FB rate was nearly cut in half, while his ISO collapsed to below .200. He was still a strong fantasy performer thanks to hit 29 steals, but this was not the same Tatis as his first three seasons. However, Statcast suggests that perhaps this was closer to the pre-surgery version than it appears, dramatically underperforming both his xBA and xSLG. His BABIP fell to a career low despite a more groundball heavy profile, though while his maxEV matched his 2020 season, his Barrel% slid to a career worst. How much of the decline in power was due to the shoulder and how much was just some regression after monster power during his first three years, we’ll never know.

What’s weird here is that you might look for an improved second half as his shoulder strengthens, but it was actually the opposite. He posted a significantly higher ISO and HR/FB rate in the first half, though it was really just a weak July and August, as he picked it back up in September. The xwOBA underperformance is encouraging, but it’s anyone’s guess whether he’ll actually get all his power back.

It’s just too funny that the biggest and fifth largest xwOBA underperformers also ranked second and third (not respectively, order is reversed) in wOBA. So the best hitters should have actually been even better last year?! Ronald Acuña Jr. posted the league’s second highest wOBA and xwOBA, and underperformed that xwOBA considerably. But this has actually been a pattern for him. He slightly overperformed during his 2018 debut, but ever since, he has underperformed every season since. He actually underperformed by nearly the same degree in 2022 as he did in 2023!

What actually surprises me here is that he posted an unbelievable 121.2 maxEV, the highest in the league and fourth highest historically, along with an elite 15.3% Barrel%, but only posted a 24% HR/FB rate. I would expect that combination to produce a higher HR/FB rate, which is probably how Statcast arrives at its higher xwOBA.

There were some interesting trends going on this year for Acuña Jr. as well. His strikeout rate was more than cut in half, an improvement you almost never see. Plus, his FB% hit a career low to a mark you just wouldn’t expect from an elite power hitter. So it’ll be interesting to see where those two rates end up this year and if his maxEV and Barrel% could produce a HR/FB rate breakout. We could see a push for 50 homers depending on where his FB% goes, but that will also depend on how much of his contact gains he holds onto.

After disappointing in 2019 and 2020, former uber prospect Vladimir Guerrero Jr. has his coming out party in 2021. It was the performance everyone knew was going to come one of these seasons. But then he regressed in 2022 to merely very good, and regressed again this past season to just good. The good news is that he massively underperformed his xwOBA, and hasn’t been a consistent underperformer previously. In fact, he’s always been pretty darn close to his xwOBA, so he’s an important player to be aware of such underperformance.

Somehow, some way, Guerrero Jr. only posted a 14.5% HR/FB rate, despite an elite maxEV and a Barrel% in the low double digits. How is that possible?! Statcast is screaming that he got super unlucky and Steamer may actually be listening. Steamer’s projection is seriously bullish, projecting him for the second highest wOBA of his career, which is even higher than last year’s xwOBA. It’s the type of performance we know he’s capable of and he may very well deliver at what might be his cheapest draft day cost in years.

Here we go, this might be a much more useful list, as some of these guys are undoubtedly going to cost a pretty penny on draft day.

TJ Friedl was a wonderful surprise for fantasy owners, hitting 18 homers and swiping 27 bases. He’s a great example of a free agent gem who may have won leagues. But…was it all a dream where you used to read Word Up! Magazine? He handily overperformed his xwOBA, and not only did so, but his xwOBA suggests he was actually a well below average hitter. That’s actually unexpected, as his .308 BABIP doesn’t stand out as being inflated, and he mustered just an 11.4% HR/FB rate and .189 ISO. Clearly no one would think twice about a hitter posting those numbers.

But perhaps he deserved a significantly lower BABIP. He posted the fifth highest IFFB% among qualified hitters and recorded a FB% well above the league average. That’s a lot of pop-ups, actually 14th most in baseball. With a below average LD% too, it seems like he must have had fortune on his side to post an above average BABIP.

The 11.4% HR/FB rate and .189 ISO look quite reasonable, right? Not when you cross-reference with his Statcast metrics! He posted just a 107.1 MPH maxEV, but even worse, he posted just a 3.2% Barrel%, which is less than half the league average. So does that mean he’s at risk for major regression this year? Not necessarily. It’s pretty clear that this is a home ballpark thing. Great American Ballpark is by far the most favorable park in baseball for left-handed home runs, and sure enough, Friedl posted a HR/FB rate at home that was nearly triple his road mark. Since he’s still a Red, we don’t have to worry as much about xwOBA regression, but it’s still worth keeping in mind. If anything, he looks like a guy to bench on the road if you’re in a daily transactions league.

Jose Altuve has made a living overperforming his xwOBA. You’d think by now we’d have an Altuve boost built into the equation since he’s clearly doing something not captured! Since 2015 when xwOBA has been available (nine seasons), he has overperformed his xwOBA in eight, with the only season he failed to coming during the short 2020 season. That said, this was the most dramatic overperformance, so that’s still a bit concerning. xwOBA overperformance or not, it’s pretty impressive that he posted the third highest wOBA of his career after returning from thumb surgery.

There are some other red flags here, including a strikeout rate that jumped to the second highest mark of his career, driven by an increased SwStk%. His IFFB% also jumped to the second highest of his career, which doesn’t match at all with a BABIP that finished highest since 2018. I still wonder how he has managed all these above average HR/FB rates given sub-110 MPH maxEV marks and mid-single digit Barrel% marks that have just recently gotten into the high single digits. He’ll be 34 years old this season, I’d be nervous drafting him at his ADP of 37.

You know how I feel about Isaac Paredes after plopping him into the sixth tier of first basemen, surrounded by Josh Bell and Alec Bohm. The one-time top prospect looks to have made good on his promise, but it looks like smoke and mirrors. If you thought Friedl had popup problems, Paredes’ are even worse! It explains the .257 BABIP here, and yet Statcast thinks he deserved an even lower batting average.

That’s probably because of his power that led to much better results than expected. Just like Friedl’s combination of maxEV and Barrel% didn’t exactly suggest much of a power hitter, Paredes’ doesn’t match a mid-teens HR/FB rate. His 5.9% Barrel% was well below average and yet somehow resulted in a .238 ISO. It’s hard to imagine that happening again without him increasing his barrel rate, but since he was never a big-time power prospect to begin with, I see no reason to think that’s going to happen. So, he doesn’t steal bases, isn’t going to help your batting average given his poor-BABIP producing batted ball profile, and is likely going to suffer some serious power regression. Oh, and he posted a negative UZR at third base. On the Rays, that’s a recipe for becoming a bench player.

Geraldo Perdomo rode a BABIP hot streak in April to full-time at-bats, but his luck eventually reversed course and he ended up posting an xwOBA almost identical to his 2022 season when he posted just a .253 actual wOBA. He should get together with Massey to work on their swings as Perdomo is also hitting an above average rate of fly balls, but without the power to actually benefit.

He did post a positive UZR which could increase his leash as an everyday player, but there’s a real chance that wOBA drops under .300, and if it does, he may be at risk of getting benched, no matter how good he is defensively.

It was cool to see Cody Bellinger rebound, as if his last three seasons just never happened! But was it really real? Sure, he was better than the last two years, but Statcast thinks he dramatically overperformed. One obvious place is in his BABIP, as he posted a career best, despite an almost identical batted ball profile to his career average, which is heavy on fly balls and popups.

While his power was better, it still remains missing in action after what we witnessed during his first four seasons. His maxEV did increase a bit from the last two seasons, but failed to breach the 110 MPH level, and even worse, he posted a career worst Barrel%! That doesn’t make me optimistic that all his issues have been solved. Moving forward, obviously his projection is going to be heavily influenced by the team he ends up signing with. Still, I think there’s a good chance he ends up overvalued given his outwardly big comeback story in 2023.

Gee, Matt McLain is the second Red on the overperformer list! The 2023 rookie and former top prospect enjoyed an excellent fantasy campaign over about two-thirds of a season. Of course, Statcast suggests it was worse than it looks. The most obvious place to start is with his absurd .385 BABIP. That ranked third among all hitters with at least 350 at-bats (245 hitters). It helps explain why his xBA is a full 0.035 points lower than his actual batting average. Sure, he posted a solid batted ball profile, heavy on liners, balancing grounders and flies, but in no way does it justify a BABIP so inflated. That means that despite hitting .290 in 2023, there’s a real chance he is either neutral or actually hurts your team’s batting average this season.

His power seemed a bit more real in my eyes, as he posted a 109.9 MPH maxEV and 10.8% Barrel%, both solid numbers. When combined with calling the second best right-handed home run park home, it doesn’t seem like a 17.4% HR/FB rate and .216 ISO are that crazy. Like Friedl, McLain was far better at home, validating the home park boost.

What I find interesting here is that McClain posted a 28.5% strikeout rate, which is pretty high, but it came with just a 10.5% SwStk%, which is actually pretty decent, especially for a power hitter. That usually is a result of passivity, where the hitter takes a lot of called strikes. Sure enough, he posted the 12th lowest Z-Swing% among the 245 hitters with at least 350 ABs. The good news is that it seems more fixable than contact rate problems, and reducing his strikeout would result in more balls in play, which means more home runs, and other counting stats. Clearly with an ADP of 62, fantasy owners love him, and while I worry about BABIP regression, I think there are other upside paths that could offset it.