The 27-year-old Dominican Republic native is coming off a strong 2017 season in which he hit .300/.338/.454 with 16 home runs across 112 games for the Yankees. Though he played second almost exclusively for the Yankees, Castro started 836 games at shortstop for the Chicago Cubs from 2010 to 2015.
His contract calls for salaries of $10.9 million in 2018, $11.9 million in 2019 and $16 million in 2020, which is a club option year, per Spotrac.
That's a concern for the Marlins, who are trying to significantly reduce payroll—an aim that was the main driver behind the Stanton deal.
In October, Barry Jackson and Clark Spencer of the Miami Herald reported the team set a $90 million payroll target for next year. Two of the players listed among the trade options, Stanton and second baseman Dee Gordon, who was traded to the Seattle Mariners on Thursday, have been moved.
In theory, Castro's versatility in the field should increase the number of possible suitors, but he's accumulated negative defensive runs saved figures at both middle infield spots, according to FanGraphs.