Xander Bogaerts’ very bad second half

Generally speaking, things are going well right now for the Red Sox even considering yesterday’s frustrating loss. Obviously, this has been something of a roller coaster season and we’re not all that far removed from an unfathomably disappointing stretch. Right now, though, things are good. They’ve won six-of-seven, including two huge games over the Orioles. The rotation is starting to look like a group that can be featured in a postseason run. The bullpen....well, let’s not talk about them. The lineup has been mostly clicking, particularly towards the bottom with Sandy Leon and Andrew Benintendi. And so, with all of this positivity, I have of course chosen a negative topic to talk about.

Amidst all of these bright spots, Xander Bogaerts has stood out lately as the complete opposite. Now, just to be clear, if the season ended today we’d still look at this year as an overall positive for the Red Sox shortstop. He’s taken another clear step forward defensively. Plus, even with this extended slump that we’ll get to in a second, he’s hitting .310/.365/.448, good for a 116 wRC+. It’s not quite as outstanding as it was a few weeks ago, but it’s still obviously a really good season.

Now, to the bad stuff. To put it bluntly, Bogaerts has been really, super, very bad in August. We’re only talking about 61 plate appearances, but he’s hit .180/.227/.180 in the month, good (bad?) for a 4 wRC+. Four. I don’t think I need to tell you how bad that is. In case you aren’t entirely familiar with triple-slash-lines, the fact that the first and third numbers are the same means he has zero extra-base hits. That’s not ideal. Really, we can trace this back to the entire second half. Since the All-Star Game, he’s hitting .260/.300/.374 for a 76 wRC+. This is over a still-small but more reasonable 135 plate appearances.

There are two clear issues that have plagued Bogaerts over this stretch, whether you look just at August or the second half as a whole: Power and plate discipline. That probably seems pretty obvious, and it is. Those are the two main portions of offensive performance, so struggling in both areas means you’re almost certainly not going to produce at the plate. Starting with the power, Bogaerts has gone from a .146 Isolated Power in the first half to .115 in the second. And, again, a .000 mark in August. For context, that is essentially going from Francisco Lindor to Martin Prado in terms of power.

What’s strange is that his batted ball profile doesn’t really like someone who has seen his power plummet of late. His ground ball rate is actually significantly lower in the second half than it was in the first, with his line drive and fly ball rates going up. Furthermore, he’s been pulling the ball more, which should be particularly helpful for a righty who calls Fenway home. That’s not to say there aren’t issues here, specifically his quality of contact. Per Fangraphs’ contact-quality metrics, Bogaerts’ hard-hit rate has fallen significantly in the second half.

The bigger deal during this slump, though, has been the shortstop’s plate discipline. One of the biggest keys to Bogaerts’ big first half was the fact that he paired the low strikeout rate he carried in 2015 with an average walk rate right above eight percent. Both numbers have gone down since the break. To wit, he’s striking out 18.6 percent of the time and walking under four percent of the time in the second half. For what it’s worth, both of those numbers are a little worse in August.

The reasons for this are relatively simple. The pitchers are making an adjustment against Bogaerts, and he hasn’t successfully completed the adjustment on his end. For one thing, pitchers have stopped throwing him so many fastballs, replacing it with a slight increase in breaking ball usage and a more significant increase in other off-speed offerings. These aren’t particularly eye-opening increases, but as you can see here there is a noticeable change from month-to-month.

The more interesting change is how pitchers are approaching him in the zone. Be prepared from some zone plots. To start, take a look at the simple plot showing the pitch locations he’s faced.

So, the biggest takeaway here is that pitchers are being more conservative against Bogaerts in the second half. Put another way, they are avoiding the inside part of the plate. Going back to the power segment above, the fact that he is pulling the ball with this kind of usage coming against him can help explain the lack of hard contact.

Going back to the plate discipline, though, this is the most pertinent plot.

This is a plot that shows the pitches that Bogaerts has swung at in the first half vs. the second half. The takeaway for me is that he is chasing way more balls on the other half of the plate. Obviously, chasing any pitches is going to make both the strikeout and walk rates much worse. On top of that, it’s really hard to make good contact with pitches that miss off the outside part of the plate, again going back to the power issue from earlier.

This slump from Bogaerts is a weird mix of small sample size noise and legitimate adjustments being made. There’s no way he’s this bad, particularly just looking at what he’s done in August. With that being said, pitchers saw how much success he had in the first half and started treating him like a great hitter. That means seeing more breaking and offspeed pitches as well as more pitches on the outer half of the plate. Bogaerts has continuously made adjustments throughout his pro career, and if he’s going to continue to be the near-elite player he was early in the year, he’ll have to make one more.