Grandal, 31, was the best catcher available in free agency. He is coming off a fine year with the Milwaukee Brewers, with whom he had to settle for a one-year pact in 2019. He hit .246/.380/.468 with 28 homers and 77 driven in. It was his fourth straight season with 20+ homers. While his catching has been criticized due to some high-profile mistakes in the postseason, the two-time All-Star once again proved himself to be one of the best pitch-framers in the game if not the best. Between the bat and the glove he has a claim to being one of the best all-around catchers in baseball.
The signing leaves open the question of what happens to James McCann, who was himself an All-Star this year. It's not that hard a question, of course, as Grandal is a far superior catcher to McCann in every respect. The Sox could make McCann a backup. Alternatively, they could try to trade him to fill other holes on the roster.
The White Sox finished 72-89 in 2019 but are showing signs of coming out of rebuilding mode and into contention mode. This signing pushes them a big step into that direction.