What to make of Matt Carpenter’s first base defense

Seemingly out of nowhere, in the tradition of outfielder-turned-second baseman Skip Schumaker, the St. Louis Cardinals shifted 2012 Rookie of the Year candidate Matt Carpenter to second base, a position he had only played for eighteen total innings in professional baseball.

Among baseball’s nineteen second basemen in 2013 who played enough innings to qualify for leaderboards, Carpenter was average to slightly below average. He was at the exact median in Defensive Runs Saved, and he was a touch below average, ranking 15th of 19, by Ultimate Zone Rating per 150 games. But Carpenter’s mediocre defense did not destroy his overall value—second basemen are not necessarily expected to have high-octane offensive performances, and thanks to a 146 wRC+ in 717 plate appearances, Matt Carpenter was the most valuable second baseman in baseball by FanGraphs Wins Above Replacement, trailing only Robinson Cano by the Baseball Reference version.

From 2014 through 2016, Matt Carpenter was primarily intended as a third baseman (2016 was a preview of his 2017 position, but this was largely a domino effect borne of injuries and a desire to get Jedd Gyorko in the lineup). Among the 25 third basemen with over 2,000 innings at the position during that three-year stretch, Carpenter ranked 19th by Defensive Runs Saved and 20th by UZR/150.

Carpenter’s worse defensive numbers at third base than at second base seem counter-intuitive: virtually all sources on the matter would argue that second base is the more difficult position of the two. There are a number of potential explanations here, the most obvious of which is that defensive metrics in particular need far more than one season to be considered reliable (even the three seasons of third base data leave something to be desired). There’s also the matter of aging—natural defensive ability tends be immediately in decline and from the beginning of 2013 to the end of 2016, Carpenter went from a hungry twenty-seven year-old to a nearly thirty-one year-old who at least merited consideration for a move to first base.

Although Matt Adams, not a superstar but not a Dan Johnson level reach at first base, was still an option for the 2017 Cardinals, the team instead moved Matt Carpenter to first base. The plan was to improve the overall quality of the infield by implementing Jhonny Peralta at third base and Aledmys Diaz at shortstop and, well, at least the Kolten Wong at second base thing has more or less come to fruition when health allows it.

While Carpenter’s first base defense has been the source of more than its share of criticism among Cardinals fans, the (again, limited sample size) numbers suggest he has been mostly competent at the position. Of 2017’s twenty-two qualified seasons at first base, Carpenter ranks 11th by Defensive Runs Saved and fourteenth by UZR.

These metrics vary somewhat significantly considering they are intended to measure the exact same thing. The point, however, is not that Matt Carpenter has been established as a solid first baseman, but that it is too early to view him as a lost cause on the field, particularly considering that he is still assimilating to a new position.

Unlike, say, shortstop or center field, much of the value of first base defense comes not from raw athleticism but from feel for the position. While Matt Carpenter is likely to lose a step or two over the next few seasons, he will gain experience at first base that he did not have coming up through the minor leagues, as he was primarily a third baseman.

After nearly identical defensive contributions per FanGraphs in 2013 and 2014, Carpenter’s defense has declined in each of the last three seasons. But his 2017 decline is at least partially misleading—the decline is exacerbated by the position adjustment for first basemen, which significantly punishes all first basemen for playing an easier position. For instance, Albert Pujols is easily the best defensive first baseman of the Defensive Runs Saved era (since 2002) by the metric, and he only had one season, a 2007 campaign in which he had the best defensive season of any first baseman during this time, in which he was not considered a net negative defensively thanks to his positional adjustment.

Carpenter is getting worse defensively in the sense that he is producing less defensive value for the Cardinals. By playing first base, it means that nobody else can, and a larger number of potent offensive bats are capable of playing at first base than at any other position. This doesn’t necessarily mean that Matt Carpenter is a worse defensive player than he was before (though he probably is, as most players are worse defensively at 31 than at 27)—it means that he has a more limited role.

The construction of the St. Louis Cardinals in 2017 frequently made playing Matt Carpenter at first base the logical move, particularly following the trade of Matt Adams to the Atlanta Braves. Paul DeJong and Kolten Wong are at least temporarily cemented in their infield positions, and when Jedd Gyorko is healthy, it could be argued that with Carpenter, the Cardinals are playing their four best hitting infielders as their regular lineup. Maybe Jose Martinez or Luke Voit could play first base, Carpenter could play third, Gyorko could play second...but this probably doesn’t represent much if any offensive improvement, either.

Things have changed a bit with recent injuries, most notably that of Jedd Gyorko. Although the Cardinals were initially hesitant to move Carpenter, even temporarily, to third base, he has recently logged considerable time at the hot corner while Jose Martinez has earned starts at first. The defensive capacity of the infield probably declines from the season’s default—Gyorko has appeared adept at third base and Jose Martinez is primarily an outfielder by trade—but the Cardinals believe (probably correctly) that Martinez is an offensive upgrade over, say, Greg Garcia.

If Matt Carpenter were on the Chicago Cubs or Cincinnati Reds, he wouldn’t start over Anthony Rizzo or Joey Votto, but he would find his way into the lineup. Perhaps he would be a defensive liability, but Carpenter would be able to make up for this with his offense, which has progressed throughout 2017 in even more obvious ways than his glove. Carpenter’s defense is more tolerable than exciting, but given his bat, this is enough to justify putting him wherever in the lineup he fits.

If a true, potent first baseman somehow became available to the Cardinals, the Cardinals should pursue such a player, but this is not a reflection on Matt Carpenter’s lack of ability to play first base at least adequately. Rather, it speaks to his ability to handle second or third base well enough for the Cardinals to improve their offense around him.