Dissecting Tommy Pham’s Slump

Exactly five weeks ago, VEB’s own Bclemens6 penned a great analysis piece entitled “Tommy Pham is Trouting.” As he wrote of Pham back on May 15th:

Today, he’s eleventh in the majors in WAR. It’s reasonable to ask whether he’s now the best center fielder in the NL, something that would have seemed pretty silly last May. By most projections, he’s just a hair short of AJ Pollock, but it’s very close, and Steamer over at Fangraphs even has Pham ahead. It’s an exciting time to be a Pham fan, that much is for sure.

A simpler time, but certainly an exciting one indeed. Pham would play later that night, capping off a three-game skid in which he went hitless with a wRC+ of negative 47 over 14 plate appearances. (For context, the league average mark for wRC+ is positive 100.) Of course, even Mike Trout is not immune to such 0-fers. In fact, he was simultaneously in the midst of a six-game hitless streak of his own. Since the final day of his “mini-slump”, Trout has rebounded and then some by posting utterly absurd video game numbers: a .388/.504/.827 slashline en route to a 253 wRC+, a whopping 153% above average.

Pham, meanwhile, has had no such luck recovering from his slew of rough games. Juxtapose his offensive stats from before May 20th to those from that date onward.

One of these players finds himself among the elite ranks of all Major League hitters. The other has been less productive at the plate than tonight’s starter for the Phillies: Vince Velasquez.

The bottom two rows contain Pham’s BABIP (batting average on balls in play) and xwOBA, a Statcast metric that estimates what a player’s weighted on-base average (wOBA) “should have been” according to his exit velocity and launch angle numbers. These figures suggest that a sizable portion of Pham’s recent struggles can be attributed to unfavorable batted ball luck, but even his expected wOBA since May 20th is a full 108 points lower.

MLB.com’s Baseball Savant Statcast database allows users to filter statistical results based on what part of the strike zone a pitch was located in. The “detailed zones” divide the plate into the following segments as shown from the catcher’s perspective.

Baseball Savant

Upon performing numerous search queries, I spotted a troubling trend for Pham on pitches elevated up in the zone (denoted by boxes 1, 2, 3, 11, 12, 13, 21, 21, and 23). My usual warning to be aware of small, misleading small sizes still applies here, but take a look at the difference in Pham’s performance on elevated pitches.

Isolated power (ISO), calculated by subtracting a hitter’s batting average from his slugging percentage, is essentially a hitter’s average number of extra bases per at-bat, meaning that Pham has tallied zero (0!) extra-base hits on pitches up in the zone as of late. Statcast’s expected ISO for Pham is still only a mere .073 while the MLB average ISO this season is .238 on elevated pitches, more than triple Pham’s power output.

Despite the fact that opponents are beginning to pitch to Pham higher in the zone with a bit more frequency, he is swinging almost four times less often in addition to taking fewer offerings for a ball. Even with this uber-selective approach to high pitches, he is virtually making an identical amount of contact on these swings as beforehand.

When bat does meet ball, Pham’s contact quality has also deteriorated as evidenced by drastically lower exit velocity numbers. With an average launch angle of six degrees lower, he is also no longer driving these elevated pitches into the air where they are much more likely to do damage in the form of extra-base hits.

The aforementioned Baseball Savant also develops “radial charts” that allow us to visualize the effectiveness of each batted ball, as certain exit velocity and launch angle pairings tend to yield more productive results than others. The first chart displays Pham’s batted balls on elevated pitches from May 19th and prior while the latter shows data from May 20th and later.

These graphics probably appear to be nothing more than polychromatic gibberish if you aren’t exactly sure how to interpret them. Dots placed higher up on the image were hit at a higher launch angle. Likewise, the closer a dot is to the edge of the radian, the harder its exit velocity.

Note how many of Pham’s batted balls in the first chart strike the ideal balance of being hit very hard but not popped up or pounded on the ground. These so-called “barrels”, boasting a league-wide wOBA of 1.300, are the holy grail of Statcast’s batted ball classifications. The sample sizes must be taken into account, but 30% of Pham’s contact on high pitches resulted in one of these coveted barrels early in the season. Since May 20th, he has yet to hit another barrel and has just one lonesome batted ball found in the strip of the chart labeled “solid contact.”

Pham has observed a spike in “topped” balls to go along with his plummet in barrels. Former VEB writer Ben Markham described each of Statcast’s six batted ball types in his breakdown of Aledmys Diaz’s hitting woes last year.

Topped: This is the opposite of hitting under the ball. Topped balls represent any batted ball under about -5 degrees. It also represents batted balls above that line, but below the velocity and/or angle requirements of being a flare or burner.

Topped balls have been the second least productive of the six groupings in 2018 with a measly .162 league average wOBA. Pham’s rate of topped batted balls has swelled from 10% to 36%, a concept illustrated by the dots located further down on the second chart.

Needless to say, Tommy Pham has some adjustments to make. He has been less aggressive–and less successful–in squaring up and driving the elevated pitches he used to absolutely pummel. It is too early to frantically press the panic button on a player who still projects to be the third most valuable centerfielder in all of baseball going forward. Pham’s life story and career arc has been defined by a need for resiliency and adaptation, which he could stand to tap into right now to prevent pitchers from further capitalizing on his flaws.