Russell, ranked baseball's No. 3 prospect by Baseball America, came to the Cubs from the Oakland A's last season in exchange for Jeff Samardzija and Jason Hammel. He has hit .300 with an .897 OPS in four minor-league seasons.
Castro is under contract in Chicago until 2019 but has said he would willingly switch positions if one of the team's prospects was better suited as shortstop. The 25-year-old led the National League in errors by a shortstop for three straight years from 2011-2013. He is batting .323 in 2015 and has committed one error.
- Alex Putterman