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The new Yankee second baseman is Starlin Castro. Castro was traded to the Yankees last night, filling a position that was previously expected to consist of a Dustin Ackley/Rob Refsnyder platoon. Yankees GM Brian Cashman shed light on his rationale for the trade:
Cashman on Castro: "He looked like a different player after the position change." Castro had great numbers after moving to 2B on August 4.
— Mark Feinsand (@FeinsandNYDN) December 9, 2015
A "different player" is a strong understatement. Castro was one of the worst big league regulars up until his position switch (which, according to the game logs, happened on August 11, not August 4), with production approximately 50% worse than the league average MLB hitter. Castro slashed .235/.271/.303 with a 52 wRC+ and .068 ISO in 436 PA before the switch to 2B. After the move, Castro hit .353/.373/.588 with a 161 wRC+ and .235 ISO in 143 regular season PA. According to statcast, Castro had a modest increase in exit velocity on his batted balls between those two samples, moving up about 2 mph, from 86 to 88 mph. He also improved his batted ball trajectory profile, popping up less and hitting more line drives.
Castro remains an enigma; he has been a very productive middle infielder before, particularly in 2014, where he hit to a .292/.339/.438 slash with a 117 wRC+. MLB average wRC+ for shortstops that year was 87. But he's also been unproductive in 2 out of his last 3 seasons, where he hit to a 74 wRC+ in 2013 and an 80 wRC+ in 2015, below average production even by positional adjustment.
Here is Castro's updated ZiPS projection for the Yankees next season:
ZiPS for NY Castro: 274/310/405, 98 OPS+, 2.2 WAR at 2B (2.1, 1.9, 1.8). Refsnyder 248/318/395 98 OPS+, 1.9 WAR at 2B (1.9, 1.9, 2.0, 1.6)
— Dan Szymborski (@DSzymborski) December 9, 2015
Retaining SS eligibility next year is important for Castro's 2016 fantasy value. Only 6 qualified shortstops finished 2015 with an OPS greater than or equal to Castro's .715 ZiPS projected OPS, with MLB average OPS for shortstops at .681. At 2B, production was higher: 13 second basemen finished with an OPS greater than .715, with MLB average OPS for second basemen at .705. Castro's best use on a fantasy roster next year will likely be at the SS position.