The Royals are expected to call up Duffey from Triple-A Omaha on Monday, Jon Heyman of the New York Post reports.
Duffey will move up to the majors after compiling a 3.24 ERA and 10:5 K:BB over 8.1 innings with Omaha this season. The 33-year-old made just one appearance in the majors in 2023 and wasn't great with the Twins in 2022, but Duffey holds a career 3.99 ERA and 301:85 K:BB across 284 innings as a reliever at the big-league level.