Should Jose Martinez play first base in 2018?

For the 2017 season, the St. Louis Cardinals moved Matt Carpenter to first base as his everyday position. In previous seasons, Carpenter had played non-disastrous (disclaimer: I watched Matt Adams play left field and my threshold for disaster is therefore extremely high) defense at second and third base, but with his overall defensive production declining and without an obvious candidate to play first base (while Matt Adams was and is fine offensively, he isn’t Joey Votto), the Cardinals decided to slide Carpenter to first while playing Jedd Gyorko, a man without a full-time position in 2016 despite playing enough to lead the team in home runs, at third base.

Jose Martinez did not have a starting spot with the Cardinals to begin 2017, and many fans considered him lucky simply to have a roster spot. Martinez, 28 on Opening Day, had spent over a decade in the minor leagues of five different organizations, including with the Kansas City Royals in 2016 before being designated for assignment. He was then traded to the Cardinals, where he was a below-average hitter for AAA Memphis (in 329 plate appearances, he triple-slashed .269/.326/.415, good for a wRC+ of 95 while playing non-premium defensive positions).

However, on the strength of a solid, if extremely abbreviated, stint with the St. Louis Cardinals in 2016 (a 179 wRC+ in 18 plate appearances) and a promising Spring Training, Martinez won the Cardinals’ fourth outfielder job over Tommy Pham, who had a significant edge in MLB experience.

While “Tommy Pham is better than Jose Martinez” takes didn’t exactly age poorly, it would be difficult to argue that Martinez did not wildly surpass all reasonable expectations of him entering the season. He was so impressive in his 307 plate appearances with the big-league club in 2017 that, per Rick Hummel, Martinez is a serious contender for the starting first base job in 2018.

Martinez’s 2017 statistics suggest that this is a sensible move. His 135 wRC+, while technically regression from his 2016 cup of coffee, was second-best on the Cardinals (behind Pham) among players with 300 or more plate appearances and surpassed the offensive production of such established hitters as Anthony Rizzo, Nolan Arenado, and Corey Seager. Among the 42 players FanGraphs lists as first basemen with 300 or more plate appearances, Martinez ranks tied for seventh with Eric Hosmer, the Kansas City Royals first baseman who is about to become a very wealthy man via free agency. And while Matt Carpenter was above-average, his 123 wRC+ lagged slightly behind.

On the surface, Jose Martinez appeared to be the latest benefactor of Cardinals Devil Magic™. Only once, in 2015 (in AAA), was Martinez more effective relative to his league than he was while playing at the highest level of his career. Additionally, Martinez’s .350 batting average on balls in play is well above the league average and suggests, at least on first glance, that he had an extraordinarily fortunate 2017 campaign, one whose luck is unsustainable going forward.

However, Statcast’s xwOBA, which measures a player’s “deserved” wOBA (an all-encompassing hitting metric similar to wRC+ or OPS+ but scaled differently), suggests that Jose Martinez was somewhat unlucky. While Martinez’s season wOBA was .379, 29th among the 287 players with 300+ plate appearances (a group that is disproportionately good at baseball, hence MLB teams giving them tons of opportunities to hit for them, as obvious as that sounds), among the 428 players with 100+ plate appearances, Martinez’s xwOBA of .411 ranked fifth. The only players with a higher expected wOBA were capital-e Elite hitters: Aaron Judge, Joey Votto, J.D. Martinez, and Mike Trout.

In the recent past, before xwOBA was a thing, sabermetrically-inclined fans would instinctively minimize what Martinez did in 2017; it’s nothing personal, but for such an outstanding season to come from such an unlikely source usually means the sample size was not large enough. But having more nuanced statistics to examine contact quality allows us another perspective.

Of course, because xwOBA is relatively new, it requires something of a leap of faith to trust in it. Admittedly, the logic behind it is sound—that some batted balls are more likely to results in hits than others and they should be scaled accordingly—but it is not foolproof. The 2016 xwOBA leader, Miguel Cabrera, lost sixty-one points of wRC+ from 2016 to 2017 and was a below Replacement Level player. Another top ten xwOBA hitter, Kendrys Morales, was also below-average at the plate in 2017. However, seven of the ten (David Ortiz, who retired, is the other one) were still very good hitters in 2017.

And if we are to elevate Martinez’s 2017 performance due to xwOBA, it is only fair to do the same for Matt Carpenter, who tied for 24th in baseball in the statistic among players with 300+ plate appearances, with a mark of .376. This doesn’t change the fact that, on a rate basis, Jose Martinez was a better hitter in 2017 than Matt Carpenter. But it is a reminder that Matt Carpenter is still really good, and unlike Martinez, he has an extensive MLB track record to support that he is a sincerely great hitter.

Neither Carpenter (third base) nor Martinez (corner outfielder) are natural first basemen, though either can handle the position well enough if their offensive production is high enough (which, in 2017, it was). In a vacuum, the Cardinals would and should opt for Matt Carpenter—the best case scenario for Martinez is that he is slightly better than Carpenter, but the average-to-worst case is that he is noticeably worse. There is zero chance that the Cardinals opt to keep Matt Carpenter on the bench in favor of Martinez (or Luke Voit, for that matter)—at that point, Carpenter would almost certainly either slide back to third base (which would then displace Jedd Gyorko) or be traded.

Because Matt Carpenter is under team-friendly terms through 2020, Carpenter would have a trade market, though as a player now in his thirties with diminishing defensive value who isn’t that cheap ($15.5 million per year for the next three seasons is fine; it just isn’t the league minimum), it’s not as though he’s the focal point of acquiring Mike Trout. A decent piece could come back in return for Carpenter, perhaps, but a player more valuable than a steady, strong-hitting corner infielder? Probably not.

Trading Matt Carpenter if the Cardinals knew they had an adequate replacement would be one thing, but Jose Martinez is still a question mark. Martinez had an excellent rookie campaign, and he has earned considerable playing time in 2018—perhaps off the bench and in pinch-hitting duty, perhaps as a corner outfielder depending on how the off-season shakes out. But the Cardinals should not bank on Jose Martinez as an everyday first baseman; while he might be for real to at least some degree, he is far more of a gamble than Jedd Gyorko or, to a greater extent, Matt Carpenter.