Mariners acquire Santana from Royals for pair of pitchers
Santana has struggled this year, hitting just .216/.349/.341 with four home runs and 21 RBIs across 52 contests for the Royals.
The 36-year-old switch-hitter will provide the Mariners with a veteran bat capable of working a walk and hitting for power as Seattle looks to climb back into the American League playoff picture.
Santana is a lifetime .244/.361/.433 hitter with 263 home runs and 886 RBIs over 13 seasons. He's also made stops with the Cleveland Guardians and Philadelphia Phillies.
Mills, 27, made eight appearances for the Mariners this season, posting a 4.15 ERA with six strikeouts.
Seattle drafted Fleming in the 11th round in 2021. The 23-year-old owns a 6-6 record with a 4.92 ERA and 59 strikeouts over 14 starts in Single-A in 2022.