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Xander Bogaerts has been awful against lefties

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This was not supposed to happen.

MLB: Boston Red Sox at Kansas City Royals Jay Biggerstaff-USA TODAY Sports

There have been many negative aspects about Xander Bogaerts. Even the most optimistic about the shortstop (and I consider myself in that group) can’t deny that this has been a subpar season with many, many issues. His overall line is just .266/.328/.394 for an 87 wRC+ that puts him 13 percent below the league-average hitter. He’s lost all semblance of power for most of the year, and even when he was hitting well towards the beginning of the season it was with a slap approach rather than consistently strong contact. His second half has been particularly dreadful, as he enters Tuesday with a 48 wRC+. Bogaerts has also been noticeably bad in high-leverage spots, which doesn’t help anyone’s perception of his season. He has a 70 wRC+ in high-leverage spots and has just one extra-base hit (a double) in 58 plate appearances in those situations. Amidst all of that, though, the one particular struggle that really stands out in my eyes is how poorly he’s performed against left-handed pitching.

This specific area of weakness has not been unique to Bogaerts in the Red Sox lineup. The team as a whole has struggled against southpaws, and it’s been one of the big reasons their offense has performed below expectations. That being said, Bogaerts’ issues may be the most startling. In 2016, he hit .304/.393/.480 for a 136 wRC+ in 145 plate appearances. This season, the 24-year-old is hitting .263/.324/.343 for a 73 wRC+ in 111 plate appearances. We’re still dealing with a relatively small sample size, but the dropoff is jarring nonetheless. There are some real issues to be solved, too.

As we try to look deeper into the problem, we’ll notice that plate discipline probably isn’t the issue for Bogaerts against lefty. Granted, he is not performing as well in this area as he did last year, but he’s still been fine. In 2017, the shortstop is walking in just over eight percent of his plate appearances while striking out in just over 16 percent. The strikeout rate is strong, and actually a bit better than last year, while the walk rate is average, though significantly worse than last year. That certainly hurts his on-base percentage, but not to the extent that we have an explanation for his downturn in overall performance.

MLB: Baltimore Orioles at Boston Red Sox Winslow Townson-USA TODAY Sports

Instead, the biggest issue for Bogaerts against southpaws has been with his batted ball profile, reflecting in both his power and his batting average on balls in play. This is not surprising for people who have watched him all year. After posting a .176 Isolated Power and a .337 BABIP against lefties in 2016, he’s posted marks of .081 and .305 this year. The power is particularly distressing, and it won’t be a surprise to hear that his groundball rate is up a whopping 13 percentage points (from 41 percent to 54 percent) from last year to this year. In addition to that, he is hitting the ball hard much less frequently, hitting the ball soft much more frequently, and using the pull side of the field on fewer occasions. All of this is an easy way to drain your power numbers, and to a lesser extent hurt your BABIP.

To explain why this is happening, we can find answers both in how pitchers are approaching Bogaerts and how Bogaerts is approaching those adjustments by his opponents. As for what pitchers are doing, it’s actually pretty simple. Lefties just aren’t throwing as many four-seam fastballs to the Red Sox shortstop as they were a year ago. In 2016, regardless of the count, Bogaerts was seeing four-seam fastballs from lefties at least 30 percent of the time, and often closer to 40 percent. This year, there isn’t a single situation in which he’s seen a four-seamer at least 30 percent of the time. The closer is on the first pitch, when he’s seen four-seamers 29 percent of the time. Instead of fastballs, he’s being peppered with two-seam fastballs and sliders. This alone goes a long way towards explaining his high groundball rate, as these two pitches tend to induce ground balls at a fairly high rate.

So, how has Bogaerts adjusted to these changes? Not super well! Remember when I said that he was seeing fastballs mostly on the first pitch? Well, he is not taking advantage of that. Four-seam fastballs are surely the easiest pitch on which to do serious damage, and Bogaerts is letting a lot of those pitches go by. Last year, he swung at roughly a quarter of first-pitch four-seamers. This year, he’s swinging at just 13 percent of them, per Brooks Baseball. Expanding the scope a bit, there’s another trend worth looking at with his swings. Below, you’ll see a comparison his swing rates in certain sections of the strike zone against left handed pitching. On the left (top on mobile), you’ll see 2016’s plot, while on the right (bottom on mobile) you’ll see 2017’s.

You can draw your own conclusions from what you see above, but the biggest thing that stands out to me is where he’s not swinging. Specifically, he’s not swinging at pitches on the inner half of the plate and on his hands. Obviously, that is a hard zone to hit well, particularly when you’re not seeing a ton of four-seam fastballs, but it’s also where you want to hit for power. A little more aggression from Bogaerts in this zone could lead to more power. It could also lead to an increased strikeout rate, but he has room to strike out a bit more if it leads to more power.

The Red Sox could really use a jump start against left-handed pitching, and that would include improvements from the entire lineup. However, Bogaerts would be a hell of a place to start. He’s had a startling drop from last year against southpaws (and in general) and he’s having trouble counter-adjusting the adjustments made by his opponents. The elephant in the room is the hand injury that has supposedly hampered him all year. However, both he and John Farrell have downplayed that possibility. If he’s totally healthy, he needs to make some sort of adjustment, because the Red Sox can’t afford him struggling to this degree against left-handed pitching.