Xander Bogaerts and the Slider

It has been a rocky calendar year and a half for Xander Bogaerts.

In the 2013 postseason, Bogaerts produced well when the Boston Red Sox needed it the most. The then-21 year old hit to an impressive .296/.412/.481 line along with a wOBA of .386 and a 17.6% walk rate. Although those numbers came across the very small sample size of 34 plate appearances (and were helped by a .421 BABIP), Bogaerts assisted the Red Sox in their World Series run and it looked like a sign of things to come.

However, it’s no secret that in 2014, the Sox’ rookie infielder Bogaerts struggled mightily.

Last season, in 594 plate appearances, Bogaerts posted just a .240/.297/.362 line with a below league average 6.6% BB% and above-average 23.2% K%. Bogaerts’ 82 wRC+ also tied Adeiny Hechavarria and Chris Johnson for the 15th worst wRC+ out of all 146 qualified MLB players last season.

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One would think that Bogaerts’ high strikeout rate means that he chased too many pitches. However, this is not the case, as his O-swing%—or the percentage of pitches a player swings out outside of the strike zone—stands at 28.5% and is better than league average.

In addition, his flyball rate was 41.3%, which was good enough for the 21st best total among qualified hitters. That, one would think, might lead to more power numbers, right? Nope. Perhaps Bogaerts’ 7.1% HR/FB% indicates that he had some bad luck, but Bogarts’ measly .123 ISO doesn’t exactly scream power hitter. In the end, all of this contributed to Bogaerts’ replacement-level 0.4 fWAR performance in 2014.

Obviously, the 22-year old is a lost cause now, right? One of the cornerstones of the Red Sox’ future a bust—imagine that! It must be clear as day now that he isn’t ready for the MLB level, send him back down! That must have been why Red Sox management would go out and acquire two players in Pablo Sandoval and Hanley Ramirez, who both play the positions Bogaerts plays. They’ve clearly lost faith!

OK, maybe that was a bit of overkill with sarcasm, but the point should still remain. It is nowhere near time to abandon hope on Xander Bogaerts. The reasoning Ben Cherington & Co. had with bringing in Ramirez and Sandoval was not to immediately replace Bogaerts, but to provide power to a lineup absolutely desperate for it. In Ramirez’ case, by playing left field it is even widely thought that he will be able to play more injury-free games as well.

However, now we turn to the issue that everyone would like to understand—what was the cause for Bogaerts’ struggles?

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While the youngster can speak four languages, it appears one of them isn’t slider–and there lies the answer. Bogaerts inability to handle sliders in 2014. While it’s understandable that a 21-year-old rookie would have a tough time dealing with this pitch type, which has a great disparity between the major and minor leagues, Bogaerts especially struggled last season.

FanGraphs has a great tool called pitch type linear weights which average out how many runs a certain player is worth when facing a certain pitch. Essentially, it lets us know how well a batter performed against any pitch. Using this, you find that Bogaerts’ owned the lowest wSL total (-12.2) in the Majors last season.

What’s significant about Bogaerts’ struggle with sliders is that they make up 19.31% (473 out of 2449) of the total pitches he saw all last season—obviously meaning he can’t continue to struggle with these types of pitches throughout his career if he hopes to put up respectable overall numbers. In fact, being that the slider is this large of a weakness for Bogaerts, he may likely see even more next season.

While his wSL alludes to a very poor ability to deal with sliders, just how bad is it? Upon digging even deeper, we find that Bogaerts hit just .147 (16 for 109) against sliders while slugging an abysmally low .174, as well. Of the 16 hits Bogaerts had, only three were extra base hits. What type? All doubles—here’s the longest one. To put that into context: among batters with at least 75 at bats vs. sliders, only Jean Segura—at .169—had a lower slugging percentage than Bogaerts. Obviously, this alludes to Bogaerts lack of power against the pitch, but what about his ability to recognize it?

Xander Bogaerts’ 2014 Spray Chart vs. Sliders

Here is the breakdown of every slider Bogaerts saw outside of the strike zone, followed by which pitches he swung at:

Bogaerts pitches seen outside the strikezone

This essentially is another way of showing how Bogaerts chased 33.45% (95 out of 284) of the sliders he saw outside of the strike-zone. And since Bogaerts overall saw 1381 pitches outside of the strike-zone, sliders make up for 20.56% of those pitches. Therefore this means that out of Bogaerts’ total chase rate, only 6.88% of them were on sliders. All that was done in order to prove this: the struggles with the slider for Bogaerts are not being helped by his willingness to chase the pitch outside of the strike zone.

Bogaerts swings outside the strike zone

Another place Bogaerts has a problem? His whiff/swing rate. On sliders, Bogaerts whiffs on 39.25% of the swings he takes—the highest total of any pitch he faces. That means Bogaerts whiffed on ≈40% of the pitches he swung at which can allude either his inability to recognize this certain pitch or just his inability to judge it’s break and therefore, he whiffs.

It’s easily put that Bogaerts batted poor against sliders not only as a result of chasing pitches and whiffing, but also as a result of the poor contact he put on the baseball. The contact he provided was weak, and in turn manifested itself elsewhere too, like his alarming almost 40% whiff rate on the pitch.

However, the cause for optimism is that for as bad as the youngster has been thus far with sliders, he’s been inversely as good with fastballs and changeups. Meaning Bogaerts did not struggle with everything he saw.

On fastballs and changeups, the shortstop slugged .466 and .403, respectively. While those totals aren’t overtly outstanding, they’re above league average and greatly contribute to Bogaerts’ overall totals as they make up 56.22% of the pitches he sees, with the overwhelming majority (47%) being fastballs.

Let’s look at how he handled fastballs a little closer:

According to linear weights, Bogaerts also posted a 4.1 on fastballs (wFA + wFT), which is above league average. Not to mention that of the 1152 fastballs he saw last season, 605 were outside of the strike-zone and Bogaerts swung at only 185 of them, meaning his chase rate was 30.5%. While that is higher than his overall chase rate, it is still respectable, lower than his slider chase rate, and something he will look to lower in the future. Combined with the low 15.87% whiff per swing Bogaerts posted on four-seam fastballs, it is within reason that he will only get better against these pitches and this could lead to greater successes than he already sees not only against the fastball, but overall as well.

Of course, using slugging percentage as a means for comparison shows the power, or lack of power, Bogaerts has versus certain pitches. We talked about his power issues above, but he’s hitting the ball about as hard as expected versus both fastballs and changeups. This is the reason it is too soon to give up on Bogaerts. He is not doing poorly overall, he’s doing poorly in one area: sliders.

It’s not inconceivable to imagine he could improve at hitting sliders, which is something that many hitters do as they go up the ranks. In addition, it’s not unimaginable to think that Bogaerts—who posted a wRC+ over 120 at every stop he had in the minors—will translate his much-heralded potential into something that’s real in the near future. For this reason, all hope should not be lost in the case of this Sox shortstop.

FanGraphs projects Xander Bogaerts to post a .256/.319/.406 slash paired with a .321 wOBA and 102 wRC+, which aren’t star-caliber numbers, but would represent a significant improvement for Bogaerts at the plate. If he can make the adjustments on sliders and maintain/improve how he has handled fastballs and changeups, Bogaerts will bounce back from his poor rookie season in a big way.

–Most statistics taken from Baseballsavant.com, as well as the Pitchf/x data they had.

–Whiff per swing rates taken from Brooksbaseball.net

–Other statistics taken from FanGraphs