Matt Carpenter was an interesting study before he made his major league debut on June 4, 2011.
Coming off a five-year career at TCU that included Tommy John surgery and a stint where he ballooned to 240 pounds (25 more than his current playing weight), Carpenter was selected in the 13th round of the 2009 MLB Draft. The former Horned Frog advanced to High-A Palm Beach in his first professional season and excelled in Double-A Springfield the following year, slashing .316/.412/.487 with 12 homers.
Despite the aforementioned brilliance in Double-A and subsequent success (.302/.419/.465, 12 HR) in Triple-A Memphis, Carpenter never was listed among the Cardinals’ elite prospects, partially due to his age (26 entering 2012) and his reputation of being below-average defensively and on the basepaths, as well as the notion that he lacked the power to play every day at third base.
While his minor league hitting profile carried over to the majors and his defensive and baserunning woes were proven to be blown out of proportion, the power never matched up to his hot corner counterparts. To determine this I used Fangraphs’ Isolated Power (ISO) statistic, which is simply slugging percentage minus batting average. I also looked at his homerun total in comparison to other third basemen.
20121: .169 ISO, 17th in MLB / 6 HR, T-29th in MLB
20132: .163 ISO, 13th in MLB / 11 HR, 18th in MLB
2014: .103 ISO, 22nd in MLB / 8 HR, T-21st in MLB
1 – I adjusted the plate appearance qualifier to 300 because Carpenter was not a full-time player.
2 – I compared Carpenter to other third basemen despite him playing 132 games at second base.
The .140 ISO over first four seasons (19 plate appearances in 2011) fell in line with his minor league track record of a .151 ISO. This is why I find Carpenter’s 2015 season to be so fascinating.
For those who haven’t been following the St. Louis Cardinals this season, Carpenter’s performance might have gone unnoticed. His season isn’t fascinating because he has posted the second-highest wRC+ (Weighted Runs Created Plus) of his career at 138 – in simpler terms meaning he has been 38 percent better than the average offensive player this season – but it’s fascinating because of the way he has achieved that mark.
Carpenter has more than doubled his career homerun total in 2015, pacing the Cardinals with 28 dingers. That number is the fifth-highest among third basemen (topping notable players such as Kris Bryant  and Kyle Seager ), and his ISO (.234) is fourth-best at the hot corner and tied with the Chicago Cubs’ Anthony Rizzo for 18th in the league.
To put this absurdity into some context, Carpenter entered the season hitting a homerun once every 71.4 plate appearances. This season he has been doing so once every 23.68 trips to the plate, basically tripling his homerun output.
I was curious to see how Carpenter’s power surge compared to other outlier performances since the turn of the century. To determine my sample, I hand-picked players based on a Fangraphs search who had spent parts of at least three seasons in the major leagues and had hit 25 homeruns in one of those years. After targeting their first season with 25≤ homers, I looked at their respective HR/PA rates leading up to that season and the rate during their power surge. Below is what I found3:
Asdrubal Cabrera (2011, 25 HR):
– 89.44 PA/HR before 2011, 26.68 PA/HR in 2011, 62.76 PA/HR difference
Jacoby Ellsbury4 (2011, 32 HR):
– 75.65 PA/HR before 2011, 22.88 PA/HR in 2011, 52.77 PA/HR difference
Matt Carpenter (2015, 28 HR):
– 71.40 PA/HR before 2015, 23.68 PA/HR in 2015, 47.72 PA/HR difference
Aaron Hill (2009, 36 HR):
– 67.82 PA/HR before 2009, 20.39 PA/HR in 2009, 47.43 PA/HR difference
Joe Mauer (2009, 28 HR):
– 54.27 PA/HR before 2009, 21.64 PA/HR in 2009, 32.63 PA/HR difference
Brandon Inge (2006, 27 HR):
– 47.07 PA/HR before 2006, 22.26 PA/HR in 2006, 24.81 PA/HR difference
David Delluci (2005, 29 HR):
– 40.89 PA/HR before 2005, 17.86 PA/HR in 2005, 23.03 PA/HR difference
Jose Bautista (2010, 54 HR):
– 34.54 PA/HR before 2010, 12.65 PA/HR in 2010, 22.89 PA/HR difference
3 – I omitted six players from the sample after completing research due to the PA/HR difference not being significant enough.
4 – I’ve always said Jacoby Ellsbury’s 2011 season is one of my favorite single-season performances in baseball, and this study only cemented that.
Carpenter has posted the third highest plate appearance per homerun rate in the sample, trailing Asdrubal Cabrera and Jacoby Ellsbury in 2011. His jump in power is comparable to Aaron Hill of the 2009 Toronto Blue Jays, who also more than doubled his career homerun output during his “outlier” year.
Cabrera’s ISO rose .087 over his career mark in 2011, while Ellsbury’s soared by .116. Hill’s 2009 ISO was .088 higher than his career mark, although the latter was slightly boosted by a 17-homerun 2007 season.
Is this to suggest Matt Carpenter will turn into Aaron Hill or Asdrubal Cabrera after this year? Certainly not. Carpenter’s best season by wRC+ (146 in 2013) surpasses their tops (133 for Hill, 119 for Cabrera), while his career line drive rate (25.8%) is at least five percent higher than their marks (20.4% for Cabrera, 19.9% for Hill).
Regardless of what happens from here, Carpenter’s power surge is one of baseball’s great statistical oddities and should be appreciated as such.