I think Castellanos would be a reasonable comp if you wanted to make the case for 5/$100 mm, which is what Castellanos got from the Phillies.   At the time, Castellanos had a career 114 OPS+, had been worth 12.5 rWAR in his career, and was heading into his age 30 season. He was coming off a 138 OPS+ season.  Right now Santander has a career 109 OPS+, has been worth 7.5 rWAR, and will  be heading into FA beginning with his age 30 season.  Given another 1.3 seasons of performance similar to 2