Kansas City Royals left-hander Danny Duffy will miss six to eight weeks with a strained oblique.
The Royals announced Monday that Duffy has a Grade One strain.
The injury was revealed a day after Duffy was tagged for six runs and nine hits in four-plus innings of a 10-1 loss at Cleveland.
Duffy is 4-4 with a 3.54 ERA in 11 starts for the Royals, who are 21-28 heading into Monday's game against the Detroit Tigers.
There was no indication Duffy was injured Sunday, though he stumbled toward first base attempting to record an out. In postgame comments, Duffy and manager Ned Yost did not say anything was physically wrong.
Before struggling Sunday, Duffy was coming off back-to-back wins over the New York Yankees that lowered his ERA to 2.82.
Duffy became the second Kansas City starter in the last week to land on the disabled list. Right-hander Nate Karns was placed on the disabled list Wednesday with an elbow injury and will miss at least one start.
In January, the Royals signed Duffy to a five-year, $65 million extension that keeps him in Kansas City through 2021. He was eligible for arbitration and could have become a free agent after this season.
A third-round pick by the Royals in 2007, Duffy made his major league debut in 2011. He is 40-37 with a 3.70 ERA in 145 appearances (117 starts) and made nine relief outings during Kansas City's back-to-back World Series trips in 2014 and 2015.