The Chicago clubs could be entering a city rivalry in free agency.
Keuchel, the 2015 AL Cy Young winner, authored a 3.75 ERA in 19 starts for the Atlanta Braves last season. The Toronto Blue Jays are reportedly interested as well.
Castellanos posted an .863 OPS with 58 doubles between the Cubs and the Detroit Tigers in 2019. The Arizona Diamondbacks and San Francisco Giants are also apparently pursuing him.
Both players are represented by agent Scott Boras, who's had high-profile free-agent clients over the last few years go unsigned until spring training, or in Keuchel's case last season, well into the start of a new campaign. However, a new trend is emerging this winter with two of Boras' free agents off the board already after Stephen Strasburg re-signed with the Washington Nationals and Mike Moustakas joined the Cincinnati Reds.
The Cubs are reportedly telling players that they need to cut salary before committing to any signing. The team is looking for a starting pitcher after Cole Hamels landed a contract with the Braves, and outfield help with Castellanos testing free agency.
Meanwhile, the White Sox also appear to be eyeing another hurler after striking out on right-hander Zack Wheeler despite offering more money than the Philadelphia Phillies, according to Ken Rosenthal of The Athletic.