Duffy, 28, has pitched well for Kansas City this year, posting a 3.54 ERA and 1.8-WAR in 68.2 innings over 11 starts. His absence leaves the Royals with a thin rotation of Jason Hammel, Ian Kennedy, Jason Vargas and depth options like Skoglund, Miguel Almonte, Jake Junis, Chris Young, Matt Strahm and Travis Wood.
The Royals currently sit 6.5 games behind the first-place Twins in the AL Central, good for last place in the strong division. The club was hoping to make a run in six consecutive games against divisional opponents (Detroit and Cleveland), but the loss of Duffy won’t help matters.
Duffy joins Nate Karns on the disabled list for the Royals, as Karns has been sidelined with an elbow injury. The club was also without Kennedy for a portion of time earlier in the year.