Has Jeter Lost His Swing?

After a solid but unremarkable season in 2008, doubts about Derek Jeter were starting to creep into the news much more often. People wondered if the great #2 was finally slowing down. By that point we all knew about the miserable defense; the dismal defense metric ratings, the meeting with Yankees' GM Brian Cashman about his defense, and more. So when he produced his worst full season offensive numbers of his career in 2008, there was cause for concern. Then 2009 happened, the year of the ageless Derek Jeter. He prevented his defense from decaying further, and had a monster offensive season. All combined, 2009 was arguably one of the best two seasons of his hallowed career. He successfully put all doubts on pause. Some wondered if he would have the same ageless career as his long time teammate, Mariano Rivera.  
Unfortunately for Derek, he was not able to continue his age defiance in 2010. The once great Derek Jeter was basically an average player in 2010, producing 2.5 fWAR. His defense was as porous as ever, and he now paired it with below average offense (97 wRC+). Was he a bad player this past season? Certainly not; he was arguably the third best shortstop in the American League (he still hit very well for a shortstop). He's just no longer the player that he used to be. Remarkably, he still appears to be eager to improve and work hard. According to reports, Jeter will work on rediscovering his offensive prowess by arriving at spring training early to work with the Yankees' hitting coach, Kevin Long. Perhaps 2010 was not a marker of decline after all; players can simply have down seasons if hitting mechanics get of of whack for an extended period of time. I would like to explore in this post whether or not such a glaring flaw is clear by looking at his performance in the strikezone and his ability to hit the ball to the opposite field. 




This graph shows the difference in run value, based on location, in Jeter's 2010 and 2009 seasons. It is from the catcher's perspective, and the black box represents the strikezone. Red (negative run values) indicate that Jeter performed worse in these areas in 2010 compared to 2009. Blue shows where he performed better than 2009, and white is neutral, meaning that he performed the same in white areas in both 2010 and 2009. Unfortunately for Jeter, it appears that he was worse pretty much everywhere except for a few pitches down in the zone and pitches down and away. There doesn't really seem to be a glaring hole hear, unless he changed his swing plane to hit pitches lower in the zone, but that seems unlikely. 

*The reason there is a significant amount of blue and red in the left most area of the graph (-2 on the x axis) is because hit by pitches have a positive run values, so the difference in colors just shows he was hit by pitches in different places in 2010 than 2009.

It's possible that this strikezone 'heat map' might not indicate a swing issue in the desired manner, so I decided to look at the quality of his hits based on where he hit them. My initial guess was that he was the same at pulling in the ball in 2010 as he was in 2009, but worse at going to the opposite field. 



These lines show a loess regression of run value by hit angle. The left side of the graph corresponds to the left half of a baseball field, and the right side corresponds to the right half of a baseball field. The black line is the average right handed hitter. As is expected, the average hitter is best when pulling the ball, and worst when going to the opposite field.* Jeter, unlike most players, is actually better when going to the opposite field. 
As you can see, my initial guess was quite wrong. Jeter was worse at hitting the ball to the opposite field than he was in 2009, but he was also significantly worse at pulling the ball too. The only place where there was no drop off was dead center. Much like the 'heat map' above, he was worse almost everywhere. Does this mean that there is no clear flaw in his swing that, if corrected, will resurrect his tremendous offense out of decline? Not necessarily, but this information is not encouraging for Jeter or Kevin Long. Based on the data, it seems like he's declining across the board, perhaps with the sole exception of plate discipline. Kevin Long has worked wonders before with Robinson Cano and Nick Swisher but it appears that this time, there's not a whole lot he will be able to do. 

*The reason why the lines have weird behavior beyond the -50 and 50 degree angle marks is because fair territory is only from -45 to 45 degrees (a right angle). In addition, not all of the gameday hit location coordinates mean the exact same thing in every ball park (home plate has a different (x,y) coordinates depending on the park), so at the extremes some of the angle calculations got a little weird. 

*This information was calculated using Darrel Zimmerman's pitch fx database and Ricky Zanker's run value mysql code.

This post originally appeared on www.pendingpinstripes.net