In 2013, in his first season as a full-time starter for the St. Louis Cardinals, Matt Carpenter was the best second baseman in baseball by FanGraphs Wins Above Replacement. He led all qualified second basemen in wRC+ with 146; only Robinson Cano came close with a 143 wRC+. He was precisely mid-pack among the seventeen qualified second basemen in Defensive Runs Saved, but it was his offensive acumen that allowed Carpenter to be worth 6.9 fWAR, making him one of baseball’s ten most valuable players on the season.
While Carpenter was an exceptional hitter for second base, he was “only” tied for 13th among all players. And had Matt Carpenter played first base, the position that he is expected to play in 2017, he would have tied with Edwin Encarnacion for 5th among first basemen in wRC+. His rank would fall to tied for 7th if the list were to include David Ortiz (not a qualified first baseman, but this was the only defensive position at which the regular designated hitter played in that or any season) and Miguel Cabrera (the first baseman by any reasonable estimation that the Detroit Tigers played at third base in order to accommodate Prince Fielder).
The threshold for offensive quality increases when jumping from second base to third base, as Matt Carpenter did full-time in 2014 and 2015, and it will increase again when Carpenter makes the leap from an all-purpose infielder who played roughly equal time at each of the non-shortstop infield positions to being fully entrenched at first base in 2017.
In 2013, MLB second basemen had a collective wRC+ of 91. In 2014 and 2015, when Carpenter primarily manned the hot corner for the Cardinals, third basemen had a wRC+ of 100 and 101, respectively. Over the last four seasons, MLB first basemen have had a wRC+ of 110.
The last two seasons of Matt Carpenter have been fairly similar offensively—he supplemented his 2013 penchant for doubles and his 2014 penchant for walks with legitimate home run power. They were certainly his most prototypical “first baseman” seasons—the position is synonymous with power, and while there are cases such as Joe Mauer of first basemen who don’t hit dingers, teams seem averse to it.
Over the last two seasons, Carpenter was tied for 14th among the 130 players with 1000 or more plate appearances in wRC+; his 137 is tied with Houston Astros second baseman Jose Altuve and is ahead of such notables as free agents Jose Bautista and Yoenis Cespedes. But ranking Matt Carpenter with first basemen puts him at 7th out of 20 (as was the case before, this does not include David Ortiz), just a hair above San Francisco Giants first baseman Brandon Belt.
Brandon Belt is a good baseball player, even a very good baseball player. Any reasonable baseball fan would like to have a player like Brandon Belt on his or her favorite team. But Brandon Belt is not a superstar in the same vein as Jose Altuve or Manny Machado or Buster Posey or other inferior hitters who more than close their offensive gap with far more valuable defense.
There are certain limitations to what first basemen can contribute defensively. Of the 296 qualified seasons by first basemen in the Ultimate Zone Rating era (since 2002), only 18 have resulted in a positive defensive contribution to the player’s overall Wins Above Replacement score. The best defensive season at first base, which belonged to 2007 Albert Pujols (by a lot), would only rank 47th in defensive value among third basemen. The second-best first base season, 2012 Adrian Gonzalez, would be 109th on third base list out of 290 seasons. Positional adjustments are a somewhat inexact science, but the number suggest what most had already assumed for years—that first base is less important than any other position (except for designated hitter, if you want to go that route) defensively.
Matt Carpenter has not played enough first base to draw any major conclusions about his abilities at the position. His career UZR is (barely) negative, but limiting it to 2016, his UZR is (barely) positive. Anecdotally, Carpenter seems adequate, not a tremendous liability but also a player who is clearly in the game for his offense prowess.
Regardless, Carpenter is almost certainly being moved to first base not because there are any illusions that he will be a transcendent defensive first basemen (because with the possible exception of Keith Hernandez, these players do not really exist) but because his defense at more pivotal positions has declined. He was worth negative defensive runs in 2011 and 2012—the former season included negligible playing time, but the latter is, if not a large enough sample from which to draw conclusions, large enough to at least raise some eyebrows. He had positive DRS in 2013 and 2014 (he was still a bit below average for his position, but there is value in being a passable-if-not-great defensive second or third baseman), but took a step back at third base in 2015 and was a decidedly worse fielder in 2016.
Matt Carpenter will 31 years old during the 2017 season. The aforementioned Miguel Cabrera, a borderline disastrous fielding third baseman forced to fake it at the position, seemed ancient during his 2012 and 2013 seasons, in which he was baseball’s best hitter yet only finished 10th and 4th, respectively, in fWAR due to his porous defense. In those seasons, he was 29 and 30.
The Cardinals seem to believe that Matt Carpenter would be a liability at a position other than first base, and they may be right, but keeping Carpenter at first base probably precludes him from being an elite player. Matt Carpenter is a very, very, very good hitter, but it takes amazing offensive production at first base to be as valuable as Carpenter was in 2013.
In the 21st century, only 19 first baseman seasons by 10 men (Albert Pujols, Jason Giambi, Todd Helton, Lance Berkman, Joey Votto, Carlos Delgado, Paul Goldschmidt, Jim Thome, Chris Davis, Derrek Lee) have eclipsed Carpenter’s 2013 fWAR total, and the worst offensive season of the lot came from 2007 Pujols (who, as mentioned before, was an anomalously great defender in that particular season), with a 155 wRC+. For reference, only five qualified hitters reached a 155 wRC+ in 2016 (Mike Trout, David Ortiz, Joey Votto, and Daniel Murphy eclipsed it; Josh Donaldson tied it). Carpenter’s career high wRC+ was 146 and his career wRC+ is 132.
It seems unlikely that Matt Carpenter is ever going to be a top-tier first baseman. By playing at second base, there is the chance Carpenter could fake it defensively and have another season as productive as 2013, but there is also a chance that he is enough of a disaster to cancel out his positive offensive contributions.
The move of Carpenter to full-time first baseman could be viewed pessimistically or optimistically. Pessimistically, Carpenter has probably now officially peaked as an overall player, destined to sit just below the absolute upper-echelon of MLB first baseman (it probably doesn’t help that two of these players, Votto and Anthony Rizzo, reside in the NL Central). But while his ceiling has been lowered, his floor has been raised. Carpenter will not be a defensive liability (and even if he is, he would’ve been considerably worse at another position) and while he may not be the best first baseman in the game, he should still be an improvement over the incumbents at the position, with the nice side effect of potentially improving the overall defense on the infield by implementing somebody different at third base.