Going Deep: 2018’s xwOBA Over and Under Performers

Ryan Amore dives into xwOBA over-and-underachievers from 2018.

With the emergence of statcast over the past few years, there is a truly sensational amount of data available to fantasy owners to consider when evaluating player performances. One example is expected wOBA or xwOBA. Now chances are pretty good that if you’re reading this you already know what wOBA is. But a short reminder never hurts. wOBA, or weighted on-base average, is a rate statistic that basically tries to account for a player’s overall offensive value by properly weighing each offensive outcome. It’s certainly a much, much more useful number for evaluating a hitter’s true talent than surface stats. But it’s still ultimately dependent on outcomes in other words, defense and thus more susceptible to the capricious flights of variance. And that’s where xwOBA comes in. xwOBA uses both exit velocity and launch angle to assign a hit probability to every batted ball event. Essentially it uses quality of contact to provide a summation of a hitter’s offensive value regardless of actual outcome. So it can be a useful tool in assessing a player’s inherent value as a hitter. Knowing that wOBA is intrinsically more variable than xwOBA we can use the difference between the two values to determine to what degree a hitter’s results may have been adversely or positively affected by variance. Now of course very rarely will a hitter’s actual and expected wOBA match exactly over a year. In addition, some hitters, for various reasons, are certainly more predisposed to over or underperforming their respective xwOBA. The purpose here is to simply survey which hitters from this past year had the biggest gap between wOBA and xwOBA. Without further ado let’s take a look at some of this year’s more notable overachievers based on wOBA-xwOBA differentials.


2018 xwOBA Overachievers


Name PA wOBA xwOBA Diff
Smith, Mallex 544 .344 .288 .052
Gennett, Scooter 638 .362 .313 .049
Bader, Harrison 427 .327 .281 .046
Adames, Willy 323 .328 .283 .045
Rosario, Eddie 592 .340 .297 .043
Andujar, Miguel 606 .361 .319 .042
Nimmo, Brandon 535 .386 .344 .042
Gonzalez, Carlos 504 .338 .297 .041
Dahl, David 271 .358 .318 .040
Polanco, Jorge 333 .336 .297 .039
Arenado, Nolan 673 .391 .352 .039
Camargo, Johan 524 .347 .310 .037
Chapman, Matt 616 .370 .333 .036
Herrera, Odubel 597 .315 .279 .036
Wendle, Joey 545 .338 .302 .036
Gregorius, Didi 569 .350 .314 .036
Baez, Javier 645 .367 .331 .036
Story, Trevor 656 .384 .349 .035

The cutoff here was set at 250 PA. There were a few names that appeared on this list that I opted to omit largely because I wanted to stick to names that are more relevant for fantasy purposes. I’ll refer to some early NFBC ADP. Keep in mind they are from 11/1 until 12/13. I’ll reference some xStats. They’re explained here. And lastly, for the purposes of this article, we’ll assume an average wOBA to be at or around .320.

Not surprisingly we see several Rockies on this list. I don’t think there’s really much to say about the proven commodities in Arenado and Story. The interesting name here is David Dahl. A strong finish to 2018 figures to drastically bolster his stock as we head into 2019. And that’s evidenced by his current 70th ADP in NFBC. Dahl was the beneficiary of a pretty wide wOBA-xwOBA differential of .040. Last year he had High Drive and Value Hit percentages above 13% both excellent marks. However, once we consider his near average xwOBA of .318 and below average park adjusted xOBA+ of 91.2 we could be looking at an or slightly below average hitter with Coors Field advantage.

Having now posted back to back 20+ homerun campaigns, Scooter Gennett looks to have emerged as a quality second base option. Gennett had one of the widest wOBA-xwOBA discrepancies in all of baseball last year at .049. Although I’m tempted to ring the regression bell, this is nothing new for the former Brewer who has routinely overshot his xwOBA every year dating back to 2015. A closer look shows that last year’s xOBA+ and xRAD (expected runs added) marks of 105.1 and 70.7 respectively are both short of what you’d call stellar but are certainly above average.

You’re drafting him for his speed so it may not end up mattering all that much but Mallex Smith’s batted ball data is thoroughly unappetizing. Along with a poor .288 xwOBA his 23.4% hard hit rate and 1.5 % barrel rate puts him in the bottom 4% of the league. xStats also charted Mallex with a 29.1% poor hit rate, a decidedly below average mark. But as we know speed can certainly cover up a lot of blemishes so it’s not all that surprising to see someone like Smith overshadow his xwOBA. As one of only three players to steal 40 bags last year, he won’t be sneaking up on anyone heading into next year with his current NFBC ADP sitting at 100.

While Eddie Rosario’s wOBA the past two years were comparable at .349 in 2017 and .340 this past season, his xwOBA was noticeably worse last year at a below average .297. This could be explained, in part at least, by an increase in Flyball rate (10.7 % to 12.9%) and Popup rate (23.6%). It’s worth noting too that his poor hit rate was also significantly below average at 29.4% and 31.1% in 2017 and 2018 respectively. Last year’s xOBA+ of 92.8 also indicates that he was a slightly below average hitter too. When you consider that in conjunction with his poor walk rate of 5.10%, Rosario may not be as appealing of an option.

Yankee rookie Miguel Andujar’s xwOBA mark of .319 doesn’t stand out in a good way relative to his wOBA of .361, but xStats paints a more optimistic picture. His value hit rate of 13.7% is very encouraging as are his xAVG of .300 and xOBA+ of 123.8. Though considering the OBP floor is pretty low (4.1 % BB rate) and the fact that barring injuries he should be batting toward the lower part of the NYY lineup his NFBC ADP of 63 doesn’t look like particularly sharp value.

It’s Javy’s world and we’re all just living in it. 2018 was a monumental season for the Cub’s Javier Baez.


Baez: A Tale of Two Years

Baez 2017 .326 .288 88.9 11.4 9.8 19.9 23.6 .338 .263 .453 41.6 .377
Baez 2018 .367 .331 129.6 17.1 15.2 16.5 23.6 .356 .293 .532 77 .401


As we see here 2018 was just a year of significant improvements across the xStat board for Baez. While he may have overachieved strictly according to xwOBA last year, it’s really nothing new for him, similar to Gennet he has routinely had a higher wOBA than xwOBA. I think the far more important take away here for Baez is that he was able to improve immensely on last year’s xwOBA mark from .288 to .331. You’ll still have to deal with the lack of walks but it’s awfully hard to not admire what he did to baseballs last year.

Matt Chapman’s 2018 campaign saw him post an impressive wOBA of .370, significantly overshadowing his xwOBA of .333. But taking a closer look shows there is still a lot to like with what Chapman did last year including nice gains in VH% (7.7 % to 10.6%) and xOBA+ (90.7 to 120.4) along with a big drop in popup rate (27.5 % to 20.4%). In addition, his average exit velocity of 93 was good for a top 3% mark in the league. Combining that with solid gains in contact including a drop in both K rate (28.7% to 23.2%) and Swinging Strike rate (11.5% to 8.8%) his outlook for 2019 seems very bright. Taking a quick look at his NFBC ADP reveals he could be a nice value at 99 in relation to fellow third basemen Andujar at 63.

An almost comical cavalcade of injuries to the Mets lineup last year afforded former first rounder Brandon Nimmo with ample playing time. And the results were impressive as he slashed his way to a .263/.404/.483 line. While he may not be quite as good as his lusty .386 wOBA would suggest, the encouraging thing here is that xwOBA mark itself of .344 is very good. It also doesn’t hurt that he posted a similar xwOBA mark (.353) the year prior although in an albeit limited 177 AB sample. xStats also bolsters Nimmo’s legitimacy with a xOBA+ of 137.3 and an above average percentage of High Drives (12.3%) and Value Hits (9%).

Now let’s look at the other side of the pendulum.


2018 xwOBA Underachievers

Name PA wOBA xwOBA Diff
Morales, Kendrys 471 .330 .384 -.054
Calhoun, Kole 552 .283 .335 -.052
Bruce, Jay 360 .297 .338 -.041
Panik, Joe 392 .280 .321 -.041
Sanchez, Gary 374 .304 .343 -.039
Braun, Ryan 447 .330 .367 -.037
Davis, Chris 522 .239 .275 -.036
Perez, Salvador 544 .304 .339 -.035
Pujols, Albert 498 .300 .335 -.035
Cruz, Nelson 591 .361 .395 -.034
Brinson, Lewis 406 .248 .281 -.033
Moreland, Mitch 459 .326 .358 -.032
Owings, Chris 309 .251 .281 -.030
Bradley Jr, Jackie 535 .311 .340 -.029
Votto, Joey 623 .370 .396 -.026
Ozuna, Marcell 628 .327 .353 -.026
Lucroy, Jonathan 454 .271 .297 -.026
Cano, Robinson 348 .364 .389 -.025


You’ll probably notice there are quite a few old guys on this list and for reference, recent retirees Victor Martinez and Joe Mauer also showed up near the top of this list. We’ll start with one of the more polarizing names in fantasy baseball right now in Gary Sanchez.


The Good the Bad and the Gary

Sanchez 2017 .368 .388 123.7 14.9 9.9 16.9 23.8 .337 .290 .526 52.7 .384
Sanchez 2018 .304 .343 115.7 16.9 11 21.7 27.8 .232 .218 .470 21 .305


There’s really no underselling just how atrocious Sanchez’s 2018 campaign was hitting just .186 across 374 PA. His xwOBA of .343 suggests that Sanchez wasn’t quite as bad as the surface slash line indicates but keep in mind it’s also a big drop from last year’s .388 mark. A closer look reveals a mixed bag some good things but also quite a few concerning trends as well. We’ll start with the bad. His poor hit rate jumped up from 23.8% to 27.8% (above 25% being into the bad range). Part of that may have to do with pitchers exploiting weaknesses in his plate approach – primarily his tendency to pull pitches on the outer half.  His pop-up rate also jumped up from 10.3% to 16.9%. Additionally, xStats had him at a .182 xBA and .232 xBABIP both representing a staggering decrease from his 2017 marks of .290 and .337 respectively. The Value Hits (11%) and High Drives (16.9%) were still there in good rates and his xOBA+ was very much above average at 115.7. The power is there with Gary but we’ve seen the floor and it’s something akin to a bottomless pit. Is he a candidate for so-called ‘positive regression’? Perhaps, but at his current NFBC ADP of 56, I’ll gladly let someone else find out for me.

Mets fans should breathe a sigh of relief. There’s really not a good reason to expect Robinson Cano to turn into a pumpkin heading into his age 36 season. Considering his already exceptional .364 wOBA in 2018 it’s probably best to use his outstanding xwOBA of .389 as a mark of validation rather than to anticipate even better results in 2019. It’s worth noting here that this year’s wOBA of .364 is right in line with his three prior years (.378, .358 and .360). Cano’s xStats were exceptional as well including a .342 xAVG, .369 xBABIP, .537 xSLG, 162.2 xwOBA+ and a very low poor hit rate of 18.7%.

So where did Joey Votto’s power go? Last year’s wOBA of .370 while still exceptional, represented his lowest mark of the past four years by a large gap (.413 in 2016). His xwOBA of .396 however, was still good for top three percent in the league. It’s worth mentioning that there has been a slight decline in Votto’s average flyball distance over the past few years and some discussion about possible age-related decline being a part of last year’s power outage. It’s a fair point to bring up at age 35 but it seems, on the surface at least, an unlikely sole cause to such a precipitous drop in power over a single year. Votto himself indicates a mechanical defect as the root of the issue, while Reds manager, Jim Riggleman, thinks various nagging injuries may be to blame. Whatever the cause may be keep in mind xStats had Votto pegged for 13 xHR compared to 31.7 in 2017 so the lack of power last year looks to be a legitimate result.

Another old guy. Kendrys Morales had one of the more torrid home run stretches of recent memory back in late August.  A quick look at xstats we’ll show you the power last year was very much legit highlighted by a 17.7 % High Drive rate. He’ll almost assuredly underachieve relative to his xwOBA given his extreme slow-footedness but assuming he sees regular at-bats next year he’s a viable source of power and one that you can get very late in drafts (474 NFBC ADP). Though keep in mind he’s now only UT eligible. Fun fact: he’s been in the top four percent in hard-hit rate four consecutive years going back to 2015.

We’ll continue right along with another older power hitter who is now only UT eligible in Nelson Cruz. While he was among the top three percent of the league in xwOBA at .396, it was a down year average wise for Cruz who hit below .260 across a full season for the first time in his career. Maybe the average doesn’t quite come back to the levels we’ve been accustomed to though xBA had him pegged at a .280 mark last year. Any fears of an age-related decline in power for Cruz can be quickly put to bed by a cursory glance at his statcast page which remains “lit” as the kids would say, with truly elite marks in Barrel %, exit velocity, and hard hit %.

My condolences to those who invested in Lewis Brinson in dynasty formats. His wOBA of .248 was beyond awful and combined with terrible plate discipline he was arguably one of the worst hitters in all of baseball last year. His xwOBA of .281, while better is far from inspiring and still well below average. We’re still only one full year in his career so I don’t want to bury him by any means but suffice it to say he’s still a long way off from being fantasy relevant.

Last year’s results were a little underwhelming relative to his monster 2017 campaign. But there’s definitely room for optimism moving forward for Marcell OzunaMost of his batted ball metrics, including this year’s xwOBA of .353, were comparable to last year’s marks.


A Final Disclaimer

Just to be clear I’m by no means saying here that those players who underachieved their respective xwOBA are necessarily headed for positive regression or vice versa. Expected wOBA is a useful statistic that can provide a quick summation of a hitter’s quality of contact and is but one piece of the statistical mosaic. Just like other statistics it’s best used in context relative to other data points and not alone at face value. Ultimately I think it’s best used to help validate results rather than as a purely predictive tool.

(Photo by Gerry Angus/ Icon Sportswire)


Ryan Amore

A proprietor of the Ketel Marte Fan Club, Ryan Amore has been writing things at Pitcher List since 2019. He grew up watching the Yankees and fondly remembers Charlie Hayes catching the final out of the '96 WS. He appreciates walks but only of the base on ball variety.

Leave a Reply

Your email address will not be published. Required fields are marked *

Account / Login