St. Louis Cardinals trade analysis: What have the Cards acquired in Brandon Moss?

I've always found the anonymous Player A vs. Player B quiz—where you only share stat lines and not names—to be a fun exercise. So let's start with just such an anonymous comparison:

I suppose the identities of Player A and Player B are relatively obvious given the trade the St. Louis Cardinals made this morning. The Cardinals sent lefthanded pitching prospect Rob Kaminsky to the Cleveland Indians in exchange for first baseman/outfielder Brandon Moss. That gives us one player's identity. Player A is Moss in 2015 with the Indians. Player B is 2015 Mark Reynolds, the player Moss appears to have been acquired to supplant at first base.

The Cards, in need of offense even before Matt Holliday reaggravated his quad strain on Wednesday night, gave up Kaminsky, a consensus top-five prospect in their system, for a player who is hitting worse on the season than Reynolds? Hold on a second. This is an overly simplistic exercise that is demonstrably unfair to Moss. We need to dig deeper. Moss's career stats provide a starting point and necessary backdrop.

Brandon Moss: Career Stats

Moss had at best an uneven start to his major-league career, but he seems to have figured the show out. Over the three seasons prior to this one, Moss has been a very good hitter. Moss has been both more consistent and a better hitter over 2012 through 2014 than Reynolds. Here is how the two sluggers' cumulative stats compare over that time period.

Moss vs. Reynolds: 2012 through 2014

Moss hit like a starting first baseman or corner outfielder who slots into the middle of the lineup while Reynolds hit like a bench player. Isolated Power (ISO) is a stat that excludes a batter's singles and focuses exclusively on his extra-base hits. Moss's ISO over the three seasons from 2012 through 2014 tied him Mike Trout for the eighth-highest ISO in all of baseball during that time period. That's the hitting profile the Indians traded for when they acquired Moss from the Oakland A's in December. It's also the player general manager John Mozeliak appears to be counting on showing up in St. Louis. And the various publicly available projection systems lend some support to the idea that Moss will hit more like his 2012-14 self than the 2015 version.

Moss: 2015 Rest-of-Season Projections

The forecasted hitting performance for Moss is a good bit better than the same for Reynolds.

Reynolds: 2015 Rest-of-Season Projections

Thus, Moss is a good bet to be an upgrade over Reynolds. And if the 2012-14 Moss shows up, he might even equal Holliday's production at the plate. The projection systems forecast Holliday to post a wRC+ between 129 and 131 over the remainder of 2015, if healthy. (A big "if," I know.)

Another dynamic is platoon splits. How will manager Mike Matheny deploy Moss? Is he an everyday player in Matheny's eyes like Jhonny Peralta or Matt Carpenter? Or will Matheny make an effort to get Reynolds into the lineup and regularly sit Moss like he did with Matt Adams prior to the first baseman's season-ending quad tear?

Moss: Career Platoon Splits

Moss has been used by and large against righties during his career. This has limited his exposure to southpaws. He has just 521 PAs against lefties. Given the variability in lefthanded hitters' performance against portsider pitchers this is short of the PA total necessary to make any sort of pronouncement with respect to Moss's true talent for hitting lefties. He probably is a bit worse at hitting lefties than his stats to date indicate, which means he is likely a bit worse than Reynolds against them (even if you want to point to Reynolds's more recent year-by-year platoon splits, without regressing them, as reason to believe he's gotten markedly worse against southpaws).

Reynolds: Career Platoon Splits

Lastly, there is the question of club control. The Cardinals traded for a slugger they will have for the final two months of the 2015 regular season and October, if they qualify for the playoffs. But he is more than a months-long rental player. Moss will be eligible for his final year of salary arbitration during the offseason. By acquiring the outfielder/first baseman, Mozeliak has positioned the Cardinals not unlike in 2012, 2013, or 2014, when they had depth at the corner slugging positions. If Jason Heyward leaves via free agency, the Cards can play Moss in right field, perhaps with Stephen Piscotty. If the Cardinals and Heyward agree to a contract that covers 2016 and beyond, Moss might bump Adams to the bench or trade block. Or maybe the Cardinals will turn around and deal Moss during the Hot Stove if they are able to bring Heyward back. But that is a scenario best left for the winter. With the Moss acquisition, the Cardinals have made their lineup deeper for the home stretch of the 2015 pennant race and added roster depth for 2016.

Correction: The original version of this post listed the number of at-bats Moss had against lefthanded pitchers instead of the number of plate appearances. It has been updated.