The Power of Zobrist

Ben Zobrist was once a light-hitting middle infielder. He bounced between the majors and the minors in 2006 and 2007, with poor results at the big league level. Then, halfway through 2008, at the age of 27, he displayed a stunning power surge that has not abated.

Ben Zobrist is about to put some serious hurt on a ball.

Throughout his time in the minors and in his first two stints with Tampa Bay, Zobrist had good discipline but hit few home runs. As Dave Cameron notes, this skill set does not often work well in the majors. Major league pitchers are more likely to use their superior control and are unafraid to challenge players that are not a threat to knock one out of the park. Prior to 2008, Zobrist certainly had not been a threat to knock one out, with 3 home runs in 280 major league at bats. Something changed that season. Zobrist hit 12 home runs in just 198 big league at bats in 2008, and he followed the performance with 27 in 501 at bats in 2009. How could this seemingly anomalous improvement have occurred? One in-depth article from early last season looked at how a swing doctor modified Zobrist’s approach and turned him from a singles slapper into a home run slugger.

I am skeptical about this explanation, for two reasons. First, there are hyperbolic stories every spring training about how certain players have changed their approach and the great results that will follow. These stories are not supported by empirical evidence, and the players who supposedly made significant adjustments usually end up with the same results as they have had in the past. We should be wary of “change in approach” stories. Second, picking out a success as a data point and then going back and finding an explanation is a dubious methodology. What about the others who change their swings or stances or aftershaves every season? How many suddenly turn from five homer guys into 25 homer guys? There is a selection problem here. If we pick the one who was successful and then attribute that success to recent deliberate changes, there is the risk of finding causation where it does not exist.

I wonder how often he gets called “Hanley the Manly.”

I took a hard look at Zobrist’s major and minor league statistics and noticed that if one can ignore his age at each level and look only at his raw statistics, he has had the career arc of a good prospect. He had decent, though not great, ISO in the minors (I discuss ISO in more depth in an earlier post). He also batted for a high average and displayed great discipline, hitting .318, walking 250 times, and striking out only 194 times over parts of five minor league seasons. And in his fifth professional season, he developed home run power. While many top prospects show serious slugging ability from the start, some develop power as they progress. These late bloomers show good hitting skills in the minors and learn to hit for power after a few seasons of experience. As Billy Beane was quoted, “Power is something that can be acquired. Good hitters develop power.” (Michael Lewis, Moneyball, 2004: 31.) Perhaps, like many prospects, Zobrist had power potential just waiting to be unlocked. Perhaps he simply developed it particularly late.

In the following graph, I compare Zobrist to another player who was once a light-hitting minor league middle infielder: Hanley Ramirez. The graph displays each hitter’s combined major and minor league ISO for the first six years of his professional career, with asterisks next to years where a majority of the player’s at bats came in the minors.

Ramirez was a top ranked prospect for years, consistently regarded as a sure all star. Zobrist, despite his competent hitting in the minors, was unknown outside of Tampa Bay at least until 2008. However, as the graph shows, their power developed at roughly the same rate. Consider also that Ramirez hit 27 home runs in 1538 total at bats in his first four professional seasons, while Zobrist hit 22 in 1531 at bats, also in his first four professional seasons. In Ramirez’s fifth and sixth seasons, he hit 46 homers in 1272 at bats. Zobrist hit a combined 43 in 784 at bats in his fifth and sixth seasons.

Aaron Hill practices for the Winter Olympics.

While Ramirez and Zobrist appear to have eerily similar career arcs, at least in terms of power, the big difference is in age. Zobrist’s 2004 debut at the bottom of the minors came at age 23, an age at which Ramirez was busy slugging 29 home runs and 48 doubles for the Marlins. Zobrist hit for power for the first time at 27, when good players are in the middle of their peak years. But there have been recent examples of other middle infielders who suddenly developed power in their mid-20s. J.J. Hardy hit 39 home runs in 1642 at bats over the first six years of his minor and major league career. He then hit 50 in the majors in his next two seasons, starting at age 24. Aaron Hill started as a slappy minor league shortstop, hitting 29 home runs in his first 1784 professional at bats, which spanned 5 seasons. He proceeded to hit 17 homers at age 25, and, after missing most of the next season due to a concussion, 36 homers at age 27.

Zobrist developed power even later than Hardy and Hill, and he is certainly a remarkable case. I am not arguing that we should have been able to predict his power surge. However, I believe there is a gap in our knowledge about how players learn to hit for power. Perhaps when we figure out how and why some prospects develop power and others do not, we will find that Zobrist is merely an extreme case of a general phenomenon.

Zobrist has always been a good, patient hitter. Whatever the reason for his power surge, it is unlikely that luck was the sole factor in his hitting 39 major league home runs over the past season and a half. Even if it turns out that his amazing 2009, when he led the majors in Wins Above Replacement, is the best season of his career, there is no reason to think that he will not be a very good player for the next several years.