In 2016, Karns went 6-2 with a 5.15 ERA for the Mariners in 22 games, 15 of those starts. Scouts say he has a plus fastball and plus curve. He had 101 strikeouts in 94 1/3 innings last season.
Karns started the '16 season in the Mariners' rotation, then was moved to the bullpen. He finished the season on the disabled list because of a back ailment.
Karns, who is under club control through 2020, has his best year with Tampa Bay in 2015 when he went 7-5 with a 3.67 ERA in 26 starts.
Dyson, 32, became expendable when the Royals acquired outfielder Jorge Soler from the Cubs for Wade Davis at the Winter Meetings.