Who will back up Starlin Castro in 2016?

As the weather warms in 2016, Yankee Stadium will be littered with pinstriped men whose abilities to erase question marks from their respective arsenals will steer the season toward successful or disappointing. Brian Cashman has acquired two talented position players in the past month, each of whom possesses a skillset, prospect pedigree, and ceiling to provide a type of hope in the Yankees fan base that only accompanies the arrival of youthful talent. Starlin Castro and Aaron Hicks join an offensive core that, although a year older, packed a punch in 2015, ranking second in baseball in runs scored.

Though it’s possible and perhaps expected for position battles to crop up throughout spring training and the preseason, including Carlos Beltran’s impending positional saga, a different battle looms ahead for hopeful Yankee reserves.

With an outfield stacked four-high with talented players facing their own unique challenges, from Brett Gardner’s health to Jacoby Ellsbury’s bounce-back to Beltran’s defense to Hicks’s acclimation to New York, the Yankees should be set. Beltran’s defense could erode so much that a move will be necessary, but for now the more interesting reserve situation lies at the 4 position.

The latter half of the 2015 saw Didi Gregorius cement himself as the Yankees’ shortstop of the future, while the final month of 2015 saw the Yankees make a trade for another young middle infielder to form a dynamic combination. With the departures of Brendan Ryan and Stephen Drew, Starlin Castro, now acts not only as starting second baseman, but also as the only capable backup shortstop currently on the roster. Barring an emergency, do not expect Gregorius and Castro to sit any games together.

The mystery beneath Gregorius and Castro regards who will play second base when Castro slides over to spell Gregorius. Last season, Yankees fans were treated to auditions from the top two candidates, whose performances were brief enough to represent poor jumping-off points to project 2016. However, that Rob Refsnyder and Dustin Ackley both stepped up in their 47 and 57 respective plate appearances can only be seen as beneficial going into the spring. Refsnyder’s OPS of .859 aligns with his work in the minors and his defensive improvements were such that Joe Girardi felt comfortable starting him in the decisive Wild Card game. All Ackley did last season was slug .654 en route to an OPS+ of 165, which would be higher than Don Mattingly ever achieved through a full season in his career. Dustin Ackley is not Don Mattingly, but he also did nothing to quell Brian Cashman’s long-held belief that his swing would thrive in Yankee Stadium.

Though Refsnyder has taken a lot of flack for his fielding while Ackley has been somewhat lauded for his competence at several positions, it is the former who played a more competent second base in 2015. Both have traveled similar paths to second base, leaving behind successful minor league and college careers at different positions. Ackley immediately took to the position defensively, competent but not great, while Refsnyder recorded 25 errors across two minor league levels in 2013. At Scranton in 2015, Refsnyder recorded 18 errors in a similar innings sample, before his call-up to the Bronx during which he only recorded one error over 106 innings. With an improved fielding percentage in the majors but a decreased range factor, combined with the eye test, it would seem the former right fielder has turned himself into a fine backup option at second base.

So, who should Yankees fans expect to see fielding flips from Starlin Castro when Didi Gregorius sits? The answer probably lies in Rob Refsnyder’s ability to be optioned to Scranton. Brian Cashman and Joe Girardi must be extremely eager to see whether Ackley’s offensive burst is a fluke. Though considered a virtuoso at the plate from his teen years, offensive projections do not see his performance stretching past average. Dan Szymborski’s ZiPS projects that Refsnyder, Ackley and Castro will have similar seasons at the plate, with respective wOBA of .318, .316, and .311. Baseball-reference predicts Castro and Ackley will OPS within 10 points of each other.

Though Starlin Castro’s backup has yet to be chosen, projections indicate that the decision will be difficult. Applied to the larger context, Rob Refsnyder and Dustin Ackley can be expected to trade blows throughout spring training in an attempt to grab the spot. Ackley’s juiced-up 2015 Yankees numbers, hitting pedigree, and match with Yankee Stadium give him an edge over Refsnyder despite the latter’s defensive progress, offensive competence, and high-standing prospect status. That Refsnyder can be optioned to Triple-A will almost certainly play a role in the decision, and he will need to prove early in 2016 that his transitional defensive woes are solidly behind him in order to enter the conversation at all, whether it is in spring training or in Scranton. The biggest takeaway is that the backup second baseman for the Yankees in 2016 will almost definitely have earned his job, which is much more than can be said of 2015.