Boston Red Sox: Did Xander Bogaerts change his swing?
Boston Red Sox shortstop Xander Bogaerts is off to an incredibly hot start. Is it just a hot streak or did he make sustainable changes to his approach at the plate? Early indications are that it might be real.
One series is an impossibly small sample size to draw any firm conclusions from, but the hype around Boston Red Sox post-prospect Xander Bogaerts is intense right now nonetheless. It’s no secret that Bogaerts wasn’t getting the ball in the air enough last season, and talk of changes in approach are rampant. And, it’s easy to infer that all the power he has displayed so far is due to getting on board with the launch angle revolution. But causation does not equal correlation, so we still need to ask the question: Did Xander Bogaerts change his swing?
Enter Tim Hyers:
The addition of Tim Hyers to the coaching staff brought with it an expectation that the Boston Red Sox would, collectively, get the ball into the air a little more. After all, the club had some of the lowest ranking players for balls hit between 19 and 39 degrees last year. That list included Bogaerts who was 172nd out of 180 players with 450 PA or more in 2017.
So what can we discern from the opening series in Tampa this past weekend? Bogaerts has a 310 wRC+ after four games, good for 8th in the majors. He hasn’t drawn a walk yet, but that’s mostly because he’s been murdering the ball. Six of his eight hits have gone for extra bases.
His soft contact percentage for the Tampa series was just 13.3%. That’s astonishingly low for a season-long rate, but in such a small sample has no predictive value. Besides, soft contact wasn’t his problem last year. He posted a 19.7% soft contract rate in 2017 for the Boston Red Sox, which put him just ahead of names like Anthony Rizzo and Justin Upton. In fact, his hard his percentage isn’t even all that out of whack with 2017. It was 31.4% last year as compared to 33.3% over the weekend.
Next: Optimal Launch Angle
Optimal Launch Angle?
What’s dramatically different, at least so far, is the angle the ball is coming off the bat. xStats.org defines six different types of contact. Dribblers, ground balls, low drives, hard drives, fly balls and popups. The two extreme ends of those ranges are the least productive. Dribblers encompass anything lower than 0 degrees. Popups are all fly balls hit at higher than 39. Everything in between is quality contact of some sort. This table breaks it down over the last three years:
| Launch Angle | AVG | SLG | wOBA |
| <0 | .187 | .202 | .170 |
| 0-10 | .515 | .581 | .476 |
| 10-19 | .708 | .968 | .711 |
| 19-26 | .554 | 1.270 | .734 |
| 26-39 | .323 | .987 | .517 |
| >39 | .044 | .087 | .054 |
wOBA is weighted on base average, which is a measure of the value of each ball in play relative to its run value. In short, it weights each outcome by type (a list of weights for every year can be found here) instead of assuming a linear growth in value like a double being worth twice as much as a single. So it functions as a measure of overall hitting value. And per the table above, hitting the ball between 19-26 degrees is going to give you the most run value. After that, 10-19 degrees is most productive.
It is not, however, the best range for home runs. Most home runs are hit between 25 and 35 degrees. In fact, we can expect something in the neighborhood of 60% of home runs to be hit in that range in a given year. So the best range for home runs tracked at xStats is 26-39, or fly balls.
Next: What's this mean for Bogaerts?
What does that have to do with Bogaerts?
xStats tracks data back to the beginning of 2015, so we are unable to include Bogaerts’ 2014 numbers. But what we can see is plenty for us to see a difference between his previous seasons for the Boston Red Sox and the Tampa series that just concluded.
Taking the above ranges we can combine them into various descriptive groups as measured by wOBA:
| Year | Bad Contact | Good Contact | Optimal Contact | Power Contact | Exit Velocity |
| 2015 | 52.70% | 47.40% | 19.60% | 18.00% | 87.7 |
| 2016 | 52.80% | 47.20% | 20.40% | 19.80% | 89.2 |
| 2017 | 56.70% | 43.20% | 21.90% | 18.30% | 87.3 |
| 2018 | 33.30% | 66.70% | 53.40% | 40.00% | 94.0 |
We can immediately see that his bad contact rate is significantly lower than in previous seasons with the two largest gains being in optimal contact (31.5%). Good contact and power contact increased as well, but not by nearly as much. More than half of his overall contact has been in the two highest ranges for wOBA and the results have shown it in five doubles and one home run.
Unlike last year, the ball is coming off of his bat at a much greater launch angle while improving on his average exit velocity. And while we are focusing on launch angle here, exit velocity is the more important component when predicting success. That said, Bogaerts’s exit velocities have been healthy, in the upper portion of the middle third of the league the last three years.
For whatever it’s worth, 94.0 mph would have been second to only Aaron Judge’s 94.9 last season.
Next: So what's it all mean?
Don’t get carried away… too much:
His performance against the Rays may be tantalizing, but a four game sample provides us with no real predictive value. What it does, however, is give us a reason to hope that Bogaerts has made an adjustment and will be putting the ball into the air more often. His 48.9% ground ball rate in 2017 was 21st highest in the majors, so there is plenty of room for improvement there, even if the exceptional rates he put on display in Tampa are not sustainable. And there are a lot of factors that could be feeding this hot start.
What are the coaches saying?
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Boston Red Sox manager Alex Cora has talked about being more aggressive:
“I expect Xander Bogaerts to be a better player.” Cora said. “These guys are going to take a step forward. We’re going to preach them to be aggressive. Not everybody has to take pitches. I get it. Work the count. But is it worth it to work the count now? Guys are throwing 98, 99. So you hunt for a pitch available and you do damage with it. That’s going to help us out.”
No qualified hitter swung at fewer pitches in the zone last season than Xander Bogaerts, at just 53.0%, although he wa 31st in the majors at swinging at first pitch strikes.
Tim Hyers has also discussed Bogaerts starting more upright and his first move being to shift his weight to his back foot, creating a stronger base to swing from. He’s also loading his hands lower which helps in adding a little uppercut to that swing, a la The Science of Hitting.
Next: Can Price perform in 2018?
The signs of the adjustments we wanted to see are there. If they indicate genuine change we could be in for a monster season from Boston’s starting shortstop. There’s a lot of baseball left to play. Almost all of it, actually. Even so, it’s tough not to be incredibly excited about what Xander Bogaerts is doing at the plate right now.