The Cincinnati Reds qualified for the Wild Card this year despite lacking a strong fifth starter or depth in left-handed bullpen pitchers.
Perhaps a good fit would be playing alongside Mike Moustakas again. It would certainly ease his transition into the team and the Reds could use another southpaw in the bullpen.
As mentioned the Reds lacked a strong ending to the rotation and with Trevor Bauer an unrestricted free agent they may need more help at starting pitching. Amir Garrett was solid in the bullpen but outside of him, they did not have good pitching from the left side. This is where Duffy could make a big impact.
A decent return would be top Reds prospect Michael Siani. He is a great glove and speedster with a knack for getting on base. His only full season in the minors in 2019 culminated with him swiping 45 bases, an OBP of .333, and making 18 outfield assists.
He just turned 22 so there is time for him to gain more experience while we see how the Royal’s current OF prospects shake out. Saini did play in three spring training version 1 games and was able to record a hit off Josh Hader. Hader only allowed eight hits in 19 innings this year in the regular season.
Options in the OF are needed, plus even if the KC Royals pay part of Duffy’s salary this still wipes money off the books that can be used to pursue other free agents.