Statcast Review: xBA - Noteworthy Fantasy Baseball Over and Underachievers

March 24, 2024

Jarod Rupp investigates some hitters with large positive and negative differences between their actual batting average and their expected batting average to see if any players will regress, overachieve, or underachieve in 2024 fantasy baseball.

So far this offseason, we've taken a look at hitters who improved their walk rates the most, those batters who increased their sweet spot% the most, potential stolen base contributors after pick 300, amongst other articles. This particular article will take yet another slice of the data to see what there is to see.

For those still drafting, there's still time to get it right! Below, we will look at some hitters that over or underperformed based on a comparison of batting average versus expected batting average (xBA). This information will help you make an informed decision when deciding between players come draft time.

But make sure you read until the end! Just because there is a large difference ("Diff" below) between the two numbers does not necessarily mean regression is likely. We'll discuss those batters highlighted in yellow since they are some of the more fantasy-relevant names.

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xBA Leaders in 2023 - Underachievers

Pete Alonso - .217 vs. .244

At the end of the 2023 season, Pete Alonso's numbers looked a lot like 2022's numbers. The Polar Bear even smacked six more home runs than the prior season in 29 fewer at-bats. The one glaring difference between the two seasons was his batting average. The shortened 2020 season aside, Alonso hadn't hit below .260 in his three other full seasons in the majors. So what happened last year? Well, the abnormally low batting average was likely a product of two things: injury and luck.

On June 7, Alonso was hit in the hand by a pitch from the Braves' Charlie Morton. Expected to miss nearly a month, Alonso returned after just 10 days. In the 18 games he played in June, the three-time All-Star hit an abysmal .152 (10-for-66), had a .254 wOBA, and a 60 wRC+. Maybe he came back from the injury too soon, or the Mets' postseason hopes were quickly fading, so he felt pressed to perform -- or maybe it was both -- but he bounced back in July and for the rest of the year.

We already noted that he hit six more HRs in 2023 than in 2022, but he also had six fewer doubles, so we'll call it a wash. The notable change was in his singles, dropping from 95 to 54. He may have simply been a victim of severe bad luck. His BABIP in 2023 was an astoundingly low .205. Even including that low number, he's got a career BABIP of .259, so that low BABIP from 2023 seems unsustainable.

For those in category leagues where average is scored, don't let last year's outlier season scare you off, as the 29-year-old will bounce back in 2024.

Pete Alonso leaves the yard! 💪 pic.twitter.com/mKKovDiX4l

— SNY (@SNYtv) March 9, 2024

Vladimir Guerrero Jr. - .264 vs. .291

This one was a difficult one to tackle. When digging into the numbers, specifically actual versus expected numbers, the tendency is first to look at BABIP to see if maybe the hitter just seemed to be uncharacteristically lucky/unlucky. Looking at Vladimir Guerrero Jr.'s BABIP in 2023, it was .277 while it was .289 the year prior -- not much difference. So we keep looking.

Strikeouts? Nope, K% was actually down in 2023 compared to 2022. Making less contact overall? Nope, Contact% has risen for two consecutive years now. Maybe he's not squaring the ball up as much? Nope, 11.1% Barrel% in 2023 versus 11.2% in 2022. Not hitting it hard enough? Nope, hard-hit% was also basically unchanged. The average EV is still in the 91st percentile. So what is it? Well, like I said, this one was difficult to figure out, and I can't say there is any clear explanation for it.

There are a few theories out there relating to injuries, the amount he's pulling/not pulling the ball, how aggressive he is on the first pitch, and more, but I'll offer up one more, and it might be more about his swing. One big difference I saw when reviewing the numbers was that his average Launch Angle increased 6.2 degrees, from 4.3 in 2022 to 10.5 in 2023. The sweet spot% also jumped. But HRs have decreased for two consecutive years. So, it seems like he's hitting the ball high and hard but not far enough for a HR, and instead, it's a fly ball out.

The fact that it's hard to figure out why it is happening, given that mostly nothing has changed, gives me confidence that Vlad Jr. will bounce back in 2024, at least in the batting average department. We may never see 40+ home runs again, but he's better than a .264 hitter. (FWIW, he's mashing this spring, too! .467 with three home runs and 10 RBI in 12 games).

Fernando Tatis Jr. - .257 vs. .282

Tatis is also somewhat confounding. His BABIP was .299, right around the league average and not far below where it was for him the prior two seasons. Also, out of the four seasons he's played, there were two seasons where his xBA was lower than his actual BA (2019 and 2021) and two seasons where his xBA was much higher than his actual BA (2020 and 2023), so there isn't any trend to go off of here. He, like Guerrero, was still hitting the ball hard in 2023, although not nearly as hard as in 2022 (and we all know how that season ended).

Noticeably, Tatis' GB% jumped almost 7% from the year prior, and his FB% decreased by nearly the same amount. His HR/FB% went from 32.1% to 17.0%, and Launch Angle took a 2.8-degree dip. His sprint speed is still elite, and his home-to-first speed is better than Ronald Acuna Jr.'s, so it doesn't seem like he's simply not running out ground ball outs. Whereas in the past, maybe he beat it out. My guess is that this is the Tatis we see going forward, and he'll be a perennial "underachiever," but only time will tell.

xBA Leaders in 2023 - Overachievers

Jose Altuve - .311 vs. .248

Jose Altuve should be the easiest one to explain here. He's got more history to go off than any other hitter discussed here and a pretty obvious trend that can be observed. Excluding the shortened 2020 season, going back to 2015 (when xBA first was tracked), Altuve's BA has exceeded his xBA in every season. It's usually not by a small amount, either. Up until last season, on average, his BA exceeded his xBA by 33 points. Last season, it exceeded it by a whopping 66 points; however, it was a much smaller sample size than normal.

Altuve played just 90 games in 2023, whereas he averaged 145 games in the prior seven seasons (excluding 2020). If he had played 50 more games, the gap likely would have shrunk closer to his average. Regardless, as a career .307 hitter, his .311 BA in 2023 is not abnormally high to the point where you'd say that regression is likely. On the other hand, the eight-time All-Star is entering his age-34 season, so to assume he'll hit over .300 for the foreseeable future wouldn't be realistic, either.

Expect Altuve's BA to take a small step back in 2024, but not so much because of some year-over-year change in luck or some other statistic; rather, simply because Father Time catches up to us all at some point.

Nolan Jones - .297 vs. .247

Nolan Jones' outperformance of xBA seems fairly cut and dry, too, but he doesn't have the lengthy MLB career to go off of like Altuve. Regardless, one thing stands out like a sore thumb. Not just any sore thumb, more like one of those giant, pulsating cartoon thumbs after the character smacks it with a hammer -- his BABIP.

When looking at BABIP, yes, there is a league average, and it was .297 in 2023. But caution is warranted when looking at the league average for this stat, as some players consistently over or underperform the league average BABIP, so comparing it to the player's career BABIP is more appropriate.

In Jones' case, we don't have the track record, but we know that even the best of the best in MLB history in creating their own "luck" doesn't surpass a career BABIP of .350. Jones' BABIP in 2023? .401.

To put it plainly, that number is simply unsustainable over time. That number will regress in 2024. And it probably would have in 2023 had he, like Altuve, played more games. Jones played in just 106 games at the major league level in 2023.

Looking at his minor league career, he did maintain a high BABIP throughout, so he could very well consistently have a higher-than-league-average BABIP over the course of his career, which could help buoy his BA. But to see his BA take a step back closer to his ATC projection of .269 seems reasonable. And he can still give you a 20/20 season.

A little rain can't stop Nolan Jones 👏 pic.twitter.com/X8kvV3tIQo

— Colorado Rockies (@Rockies) March 15, 2024

Cody Bellinger - .307 vs. .270

Cody Bellinger is reminiscent of Tatis, where he's been all over the map BA and xBA-wise, so it's hard to pinpoint whether or not regression is due. We're talking about a player who won Rookie of the Year in 2017, won the NL MVP in 2019, then hit .165 and .210 in 2021 and 2022, respectively. Now that's high highs and low lows.

The good things you can take away from last season are that he increased his Contact% from 76.0% to 81.2% year-over-year while reducing his K% from 27.3% to 15.6%. Although his hard-hit%, Barrel%, and Launch Angle decreased, his sweet spot% went up. He reduced his FB% by 3.5% and added it to his LD% (GB% was unchanged).

All of this is telling me he was making a concerted effort to make contact instead of launch home runs, resulting in a better average and, as they say, make good contact and the home runs will come. He still managed to increase his HR total by six despite having a virtually identical amount of at-bats in 2023 versus 2022.

He's still just 28, and I imagine he'll try to replicate last season's approach. He's done it early in his career and again last year, so I'm sold on him being able to repeat his 2023 without much regression in 2024.

Don't Assume Regression

TJ Friedl - .279 vs. .240

Friedl's recent injury dampens the mood in this section; however, I wanted to discuss him as a good-use case as to why you can't automatically assume regression. Friedl has made a name for himself as one of the best bunters in the league. Friedl had 17 bunt singles in 2023 out of 24 at-bats, good for a .708 average. Not only is he good at getting the ball down in a place that makes it difficult for the fielder to get him out, but he's also quick.

He's got a 74th percentile sprint speed, according to Baseball Savant, which doesn't necessarily jump off the page, but his 4.27 home-to-first speed is better than Oakland's Esteury Ruiz and Atlanta's Ronald Acuna Jr., each league's stolen base leader from a season ago. He also has a high contact rate, 83.4% to be exact, which is much better than the league average. But it is soft contact, as evidenced by his average exit velocity (11th percentile) and hard-hit% (fifth percentile).

Well, two-time batting champ Luis Arraez has a 29th percentile EV and third percentile hard-hit%, so hitting for a high average with that type of profile is certainly possible. Friedl's injury is to his wrist, which could hamper his ability to get the bat around, but had the injury not occurred. I believe another season around .275 was certainly within reach. Nevertheless, the point of this little anecdote was to remind you to don't automatically assume regression when comparing actual and expected stats.

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