TYA Mailbag: What is up with Jacoby Ellsbury’s power?

I really didn't need another Boston power hitter in my life.

TYA reader Shai recently sent us this question via Twitter: “Can I make a request for an article on Jacoby Ellsbury‘s power and if it’s sustainable?” This question couldn’t come at a better time. Jacoby Ellsbury hit a three run homer in the first game of Tuesday’s day-night doubleheader the Red Sox played against the Rays. That hit gave Ellsbury 21 homers on the season. In his entire professional career entering this year he’d hit only 20 homers. So, yeah, Jacoby’s hitting with a bit more pop this season. Shai can count me among those who are curious to know if the power is sustainable or not.

It’s certainly unprecedented. The table below shows what Ellsbury has done since he entered the majors. (To be consistent with the advanced stats, all of these data exclude what Jacoby did in both of Tuesday’s games.)

Apart from his cup of coffee campaign in 2007, Ellsbury has never shown the kind of power he’s had with the bat this year. In 2008 and 2009, his two previous full major league seasons, he never managed an SLG higher than .415. Entering Tuesday’s games his SLG was up around .508 and his average was the highest it’s ever been in a complete season. The big standout number is the home runs. With Tuesday’s jack Ellsbury has now exceeded in one season the entire homer output he managed in his career prior to 2011. To put this transformation into context, entering Tuesday’s games Adrian Gonzalez was a career .293/.374/.513 hitter. Ellsbury has turned himself, at least this year, from Brett Gardner into A-Gon. How did he do it?

Unfortunately, there is no clear answer in the data. The two tables below show a variety of plate discipline and batted ball statistics for Ellsbury’s career, excluding Tuesday’s game.

The data above show Ellsbury’s career ISO, BABIP, fly ball tendencies, strike out and walk rates, how he has fared against two important pitches, and his discipline with the bat. If there was evidence that the new Jacoby Ellsbury is actually a flash in the pan, it would be in the data above. Some of it is to be expected. Ellsbury’s .195 ISO this season is, obviously, his career high. But most of the data are frustratingly consistent. Ellsbury isn’t getting luck from the BABIP gods. He’s hitting more line drives and fly balls, but he’s also hitting more homers, so that’s to be expected. His strike out and walk rates are in line with past performance as well. Only a couple items jump out.

The first is that Ellsbury has been a lousy fastball hitter his entire career, until this year. Now, he’s murdering the pitch. In addition, he is also killing the cutter, something he hasn’t consistently done in the past. Given that any major leaguer will see one of these two pitches at least 60% of the time, this is a huge development. It is also a big reason why Ellsbury is suddenly producing so many homers. Home run hitters crush fastballs. Ellsbury didn’t used to crush ‘em. He’s crushing ‘em now, and the hits are leaving the park.

The other data points that jump out have to do with Ellsbury’s plate discipline. He’s swing more — and striking out more — especially at pitches in the zone. This is probably a by product of his successful year. He’s more confident, so he’s trying to connect more and showing less discipline. However, as a result of that is Ellsbury is swinging at far, far more pitches in the zone. Those pitches will tend to be fastballs. He’s crushing fastballs this year. We all know the rest.

To be able to conclude with confidence that Ellsbury’s power boost is ephemeral there would have to be evidence that he’s getting lucky somehow. This would be easiest to argue if the numbers showed an unsustainable increase in his fly ball or home run to fly ball rates. They don’t. The rates have increased a bit, but that’s to be expected. He is, after all, hitting more homers. A lucky surge would have been something in the area of 30% of his fly balls carrying for homers. The 15% he’s demonstrated this year is in line with his surge in homers, and sustainable.

As a result, the explanatory variable is the success against the fastball, and to a lesser extent his new found eagerness to swing, which is related to his successful season. The question then becomes why has a player who was genuinely a bad fastball hitter for his entire career become almost as effective against the pitch this season as Mark Teixeira (2011 1.58 wFB/C)? Unfortunately, the data don’t have the answer to that. Curtis Granderson, for example, had a 0.77 wFB/C in 2010 and has improved that to 2.10 in 2011, but his improvement is almost universally credited to his new approach at the plate. I don’t watch enough of Ellsbury to know if he’s changed his swing some how.

Russell Martin is another example of a player who has been inconsistent for his career against the fastball. Martin was a plus player against the pitch in 2007 and 2008 but has succombed to injury and struggled against the pitch ever since. Ellsbury has come back from injury this season, but that wouldn’t explain his lack of success against the fastball in his healthy 2008 and 2009 seasons.

Judging by the data available, Jacoby Ellsbury’s power surge this year is due to his incredible improvement against the fastball. Unfortunately, it is difficult to say why he has suddenly become a good fastball hitter. It could be that he’s entering his prime and becoming stronger. He could have a new approach at the plate. He could be healthy, or it could be due to something else entirely. Without more information, it is also difficult to say whether or not the change is sustainable. Speaking as a Yankee fan, I hope it’s not. In 2009 Joe Mauer saw his ISO inexplicably jump up to .222 after having been .123 the previous season before falling back down to .141 in 2010. My fingers are crossed that we see a similar reversion to the mean from Ellsbury.