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Why Andrew Vaughn Should Start Regularly in the Playoffs

by Nik Gaur

Since August 16th, Andrew Vaughn is hitting .129/.221/.165 over 95 plate appearances. That is not good no matter how you slice it, and in case you thought my premise would be something along the lines of “actually, his results have been decent lately,” you would be mistaken. His process, however, has not been nearly as bad, and I believe he is due for positive regression.

Lately, White Sox fans have been discussing potential playoff lineups, and Vaughn is often left out of them or platooned with Gavin Sheets. Of course, everyone knows that Vaughn has been instrumental to the success of the White Sox this year, especially since outfield depth has been a major issue. But, as evidenced earlier, his performance over the last month has not been good, so it makes sense to look to limit his role in the postseason, which should reward recent performance over what Vaughn might have done in May or July.

Vaughn, however, has been uniquely unlucky since August 16th. Remember earlier in the year, when many were frustrated by Yasmani Grandal’s production, but were constantly lectured to about how he was not playing poorly, and was just unlucky? Obviously, I’d think everyone would understand that view a bit more now. With respect to Vaughn, there is good news and bad news. The good: Vaughn has arguably had even worse luck since mid-August than Grandal did in the beginning of the season. The bad: you shouldn’t expect a Grandal-esque offensive outburst from Vaughn, because even if his luck were normalized, he’d still be hitting at a league-average or worse level since August 16th. I’ll explain.

For the season, Vaughn has a .308 wOBA, which is an all-encompassing Statcast metric based on his batted ball data for which .317 is the league average. His xwOBA, a similar metric that shows what Vaughn’s wOBA would be in a perfect world where everybody got exactly what they deserved without any good or bad luck, is .332 (league average xwOBA is .312). Therefore, this 24 point discrepancy would suggest that Vaughn has been slightly unlucky this season. That lack of luck, however, becomes astounding when one views the data since August 16th.

Below is a graph of all hitters with 75+ plate appearances since August 16th. The x-axis is xwOBA, and the y-axis is wOBA. In simple terms, anything below the red trend line can be considered “unlucky” over this span, and anyone above it can be considered “lucky.” Players closer to the right have performed better based on expected results, and players closer to the top have produced better results. Players both at the right and toward the top, such as Yasmani Grandal, are just really good. Over a longer, more significant sample, most hitters would begin to converge closer to the trend line.

Courtesy of Baseball Savant

Vaughn’s wOBA – xwOBA discrepancy is the second-largest in baseball since August 16th. He has a .187 wOBA, but a .292 xwOBA — that’s a massive .105 difference. It is mostly fueled by Vaughn’s almost unbelievable streak of bad luck on barreled balls (a barrel is a batted ball with the perfect combination of exit velocity and launch angle; barrels have a .500 batting average and 1.500 slugging percentage league-wide).

Below is a similar graph with the same axes and the same date range. The difference is that it only shows data for barreled balls (minimum 5 barrels across the span).

Courtesy of Baseball Savant

Vaughn has a 1.053 xwOBA over his nine barrels since August 16th. His actual wOBA on those barrels? .321. That computes to a .732 discrepancy, which is by far the largest of any player in baseball over this span (the next closest player is at .606). When one looks at Vaughn’s individual barreled balls, the overall bad luck becomes more clear. Vaughn’s last six barrels have been outs.

Courtesy of Baseball Savant

It is difficult to put into words how unlucky that is, and how frustrating it must be for Vaughn. His expected batting average on those batted balls is .644. His actual average, of course, is .000. The probability of all six of these consecutive barrels resulting in outs is 1.67%. Yet, this is exactly what has happened to Vaughn.

Here’s one of his most recent barrel outs, in case you want a better idea of what I’m talking about.

Courtesy of Baseball Savant

As I try to poke holes in my own writing, two main issues come up that I believe are valid. The first is that while Vaughn’s incredible streak of bad luck on barrels is unlikely to continue, a .292 xwOBA since August 16th is still not good. I can’t argue with that — it’s a slump — one that I’m hoping his injured list stint has broken him out of, but a slump nonetheless. His performance (and by that, I mean his batted ball data) this weekend against the Tigers will be very telling as to whether he should start every playoff game, or just certain ones based on matchups. Overall, I have been encouraged by his at-bats since he returned from injury, as his .346 xwOBA over that span is much more in line with his overall season numbers.

But what if he isn’t out of his slump, and the White Sox start him in the playoffs only for him to disappoint? What if he registers a couple of barrels in the postseason, but they, too, result in outs despite having >.500 xBAs? This, to me, is the best counter to my claims. I do not want to fall prey to the gambler’s fallacy, which is the errant belief that statistically independent events are bound to affect each other in some way over small samples. (The best example of this fallacy pertains to coin flipping: if you flip a coin twice, and it lands on heads both times, the odds of it landing on heads a third time in a row are not any different than they were before.)

In other words, Vaughn’s bad luck on barrels only means that over a long sample of hundreds, if not a thousand plate appearances, he is likely to perform closer to his expected statistics. One cannot simply plug him into playoff lineups and assume that his best swings will produce great results — while it is more likely than not that they would (which is why I want him to start), his recent outcomes will not factor into his forthcoming opportunities. The White Sox would essentially be betting on Vaughn’s luck turning, much like Grandal’s did, but there is no guarantee that the luck reversal will come in 2021.

So, we are left with a somewhat slumping but very unlucky Vaughn, an injured and/or rusty Adam Engel, Gavin Sheets, and Leury Garcia (who might start at second base) in the mix for right field and designated hitter reps in the playoffs. If the White Sox decide to make Vaughn the odd man out in certain matchups, I would understand. I just hope that his ridiculously bad luck as of late would not be the main reason for it.

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