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Cracks in the batted ball profile of Kolten Wong

St. Louis Cardinals Kolten Wong

photo by @cardinalsgifs

Kolten Wong made a very bad play last night in extra innings that arguably cost the St. Louis Cardinals a win. I’m not here to talk about Wong’s defense, though. I expressed my take on that subject in the offseason and have commented on it here and here.

Instead, I want to address Kolten Wong’s start at the plate. Through May 1st, he owns an OPS of .819, which is good for a 110 wRC+ (10% above average). His 12.2% walk rate is identical to his strikeout rate and his plate discipline statistics are still trending in a positive direction. Almost everyone has commented on his improvement at the plate, and for once it’s Wong’s bat keeping him in the lineup.

Yet, it’s not all positives for Kolten Wong. I’ve had concerns about his contact profile for some time now and he’s done very little to alleviate those worries.

Since Kolten Wong is not a power hitter, his success depends heavily on BABIP, or batting average on balls in play. The MLB average BABIP sits right around .300. Additionally, expectations for a specific player are best guided by that player’s career average BABIP instead of the league average; Kolten Wong owns a career .279 BABIP. After more than 1500 plate appearances, it’s safe to conclude he has below average BABIP talent.

When a player deviates from either league average or their career average, many jump to the conclusion that a player has been lucky or unlucky. While luck (or lack thereof) is certainly a factor, contact quality is probably more important. The advent of Statcast’s hit probability confirms that notion. While Statcast uses only exit velocity and launch angle to measure contact quality, I use exit velocity, launch angle, and spray angle.

With these variables, we can calculate xStats to compare a player’s actual performance to his expected performance. If a player outperforms his xStats, we’d call him lucky and expect regression (assuming a consistent contact profile). If a player is underperforming his xStats, we’d call him unlucky and expect improvement. Notably, this methodology does not account for speed or defensive positioning (among other factors), which are potential sources for error.

Using his batted ball data courtesy of Baseball Savant and plate discipline metrics from FanGraphs, I arrived at the following xStats line for Kolten Wong, which I compare to his actual performance.

St. Louis Cardinals Kolten Wong

As you can see, Kolten Wong has outperformed his xOPS by 174 points and xwOBA by 53 points. If he was performing at the expected levels, he’d be a significantly below average hitter. Since his expected walk and strikeout rates are near his actual levels, the difference is driven by an extremely low xBABIP and xBACON (batting average on contact), as well as a low xISO (isolated slugging percentage).

Taking a look into batted ball specifics, Wong’s 86.3 mph average exit velocity this season ranks in the bottom third of all MLB hitters with 50+ at-bats so far. This doesn’t look like a small sample size problem, either. For one, his 87.5 mph average since 2015 also ranks in the bottom third of players with at least 250+ at-bats since the start of that season. Additionally, his 86.3 mph EV this year represents a 0.7 mph drop compared to 2016, which is right in line with the league-wide drop of 0.6 mph.

As a result, Wong has been below average at generating “barreled balls” over the past few years. Basically, Kolten Wong is bad at generating strong contact.

The best contact, whether measured by wOBA or OPS, comes at launch angles between 10 and 30 degrees, which includes line drives and low fly balls. In other words, contact in the air is better than contact on the ground, so long as you can avoid high angle fly balls and pop-ups.

Unfortunately, Kolten Wong is struggling to generate batted balls in that range. To date in 2017, his ground ball rate is at a career high of 54.7% (18th highest) while his line drive rate is down to 13.2% (12th lowest). Furthermore, Wong has hit ground balls at a higher than average rate in four of his five MLB seasons/stints. Compounding the problem this year is an infield fly ball rate of 17.6%, which is 29th highest among 184 qualified hitters. Then, even when he does hit the ball between 10 and 30 degrees, he struggles to do so with authority: his 91.7 mph average exit velocity ranks in the bottom half of the MLB.

Wong’s early season results have unquestionably given him something to build on. His April wRC+ of 108 is 28 points better than his career 80 wRC+ in the season’s first month. Unfortunately, however, it appears his early success was built upon a weak foundation.

That said, there is a chance that Kolten Wong improves his contact profile. If he does, it wouldn’t be unreasonable for him to perform at or better than his historical BABIP level. That, coupled with improved strikeout and walk rates, would probably make him about a league average hitter. If he gets back to playing above average defense, then he becomes a very valuable player.

Just don’t be surprised if Kolten Wong comes back to reality and looks more like the 87 wRC+ hitter we knew from 2013 to 2016.