How much power will Kolten Wong hit for in 2015?

In November 2013, the St. Louis Cardinals traded 2011 World Series legend and incumbent starting third baseman David Freese to the Los Angeles Angels of Anaheim. The move created a vacancy at third base to be filled by shifting seven-win-second-baseman Matt Carpenter back to his native hot corner. This, in turn, created an opening at the keystone for Kolten Wong. One could reasonably say that the Cardinals' decision to trade Freese was motivated in part by creating a spot for the rookie, which would inject speed into the lineup and improve the club's defense.

Wong had shown consistent contact skill as part of a well-rounded game throughout his climb up the St. Louis organizational ladder after the club drafted him in the first  round of the 2011 Rule 4 draft. Not surprisingly, the projection systems forecast a solid rookie year for the Hawaiian, even after a rough 62 plate appearances (PA) in his 2013 major-league debut. What the projection systems did not forecast was power.

Isolated Power (ISO) is a stat designed to measure only a player's power-hitting. Unlike slugging percentage (SLG), which is calculated using singles, doubles, triples, and home runs, ISO is figured based solely on extra-base hits. ISO excludes singles from its formula. In its glossary, Fangraphs provides a handy graph by which we can measure how good a player's ISO is:

Chart from Fangraphs Glossary: Isolated Power (ISO)

Here are the ISO projections for Wong entering the 2014 season:

• VEB Community:  118
• Steamer:  118
• Oliver:  109
• PECOTA:  109
• ZiPS:  106

Even the VEB Community, with its typical optimism, projected Wong to hit for a below-average ISO in 2014. So did Steamer. By the Fangraphs ISO chart, Oliver, PECOTA, and ZiPS projected Wong to be so far below average as to be poor in his extra-base-hit batting.

As Aaron recounted in his review of Wong's 2014 season, the second baseman performed a bit below expectations. However, there was one area of his game in which Wong offered a pleasant surprise: power-hitting. The second baseman posted a .139 ISO. As the Fangraphs glossary ISO chart indicates, this was right about league average. In 2014, non-pitchers hit for a .138 ISO while second baseman collective posted a .113 ISO. Wong's ISO was roughly league average and was consequently head and shoulders above the MLB extra-base rate for those who man the keystone.

Regression is a term we see used in reference to baseball performance quite regularly—often in a negative tone. But regression can mean a player's stats are likely to go up and down in positive ways. The ZiPS and Steamer projection systems forecast a regression in Trevor Rosenthal's walk rate, that Rosenthal will walk fewer batters in 2015 than he did in 2014. They also project Lance Lynn's strikeout rate to regress upwards from a career low in 2014. In the case of Wong's ISO, though, ZiPS and Steamer forecast a regression down to .125. Is this a fair regression forecast?

First, consider that Wong's 2014 ISO was fueled by homers. Wong whacked a dinger once every 36.3 plate appearances (PA) in 2014. In the minors, by comparison, Wong hit a homer once every 49.8 PA. So it seems unlikely that the Rainbow Warrior will continue swatting home runs at his 2014 clip.

On the other hand, Wong rapped just 14 doubles a year ago; or, one in every 30.6 PA. As a minor-leaguer, Wong hit a double once every 21.3 PA. Likewise with triples—an admittedly far more volatile hit type. Last year, Wong netted a three-bagger once every 143 PA. On the farm, he posted a 3B/PA of 84.

It seems fair to assume that Wong's homer rate will drop in 2015 while his double rate will rise. As for triples, well, who knows. Put otherwise: Wong's power-hitting in 2015 will likely more closely resemble his minor-league performance with more doubles and fewer dingers. How did such a hit profile manifest itself in the minors?

Wong made his professional debut in the Midwest League after being drafted. The MWL is not known for being particularly hitter friendly. Wong posted a .175 ISO over just 222 PA in 2011. For what it's worth, that was well above the MWL collective ISO of .120.

In 2012, Wong played the entire season in the Texas League, which is known as being a batter's haven. Springfield plays its home games in Hammons Field, a ballpark that has gained an anecdotal reputation for being particularly beneficial to lefthanded hitters (just look at the Double-A numbers for Colby Rasmus, Daniel Descalso, Matt Adams, Oscar Taveras, and James Ramsey). In 2012, the Texas League-wide ISO was .133 to Wong's .119.

Wong went from well above-average power-hitting over a small sample in a pitcher-friendly Low-A league to well below-average in a larger sample in a hitter-friendly Double-A league.

Wong spent the majority of 2013 with Triple-A Memphis in the Pacific Coast League. The PCL is known as a hitter's haven, but the Memphis ballpark is relatively pitcher-friendly. That year, the PCL ISO was .144; Wong's .163. Once again, his extra-base hitting was comfortably above the league-wide rate.

What does all of this mean? It's likely that the power-hitting Wong flashed during 2014 is unlikely to manifest itself in his sophomore season quite the same way. Wong's ISO will likely be less this year than it was last, because there will be a larger share of doubles and lesser share of dingers. That being said, given Wong's track record, it wouldn't be terribly surprising if he posts an ISO closer to league-average in 2015 than his ZiPS and Steamer projection.