The club officially placed Duffy on the 10-day disabled list Tuesday, calling up Triple-A Omaha left-hander Eric Skoglund -- the Royals' No. 3 ranked prospect -- to make his Major League debut vs. the Tigers.
"This is a big time for us to turn around the ship," Duffy said. "But I know the boys are going to pick me up. I'll be fresh and ready to go in 6-8 [weeks] or whatever they say. I'm going to try and come back sooner than that. I want to win and help this team win.
"Very bummed out today, but I'm going to keep the same mentality and keep the boys in it."
Duffy began to feel discomfort last night in his right side.
"When I woke up this morning, I could barely get up," Duffy said. "It happens. It's baseball. If I get over [to first] in time, we're not even talking about this. I take full responsibility."
Duffy was late covering the base on a ground ball by Michael Brantley to Eric Hosmer. Duffy took the toss from Hosmer, but Duffy missed touching the bag before spilling to the ground.
"I overran the bag and tried to take two steps with my left foot," Duffy said. "I tried to brace to protect [my left arm]. You all saw what happened. It was probably the least athletic thing I've done."
News of the injury had Duffy's teammates shaking their heads.
"It's terrible," catcher Salvador Perez said. "Best pitcher on the team. But it's part of the game. Part of life. We've got to handle it."
Royals right-hander Ian Kennedy added, "Danny and [Nathan Karns] are hurt, and me coming back from injury. We're pretty banged up right now. But we went through this last year. It's hard to replace [Duffy], though."
Royals manager Ned Yost said simply that the young pitchers, such as Skoglund and perhaps right-hander Jake Junis, will have to step up.
"It's an opportunity for them," Yost said.
Skoglund was a third-round pick in the 2014 Draft and he is ranked as the club's No. 3 prospect by MLBPipeline.com. The 24-year-old is 2-3 with a 4.53 ERA at Omaha this season.
Fantasy spin | Fred Zinkie (@FredZinkieMLB)
Most mixed-league owners will want to retain Duffy during his extended absence, as the left-hander has allowed two or fewer runs in eight of 11 starts this season. However, those with multiple injured starters may not have the bench or DL space to wait until the second half of July for the 28-year-old to return. Shallow-league Duffy owners can check waivers for a replacement such as Zack Godley, Dan Straily or JC Ramirez, while those in deeper leagues can take a look at Dinelson Lamet, Ty Blach or Eddie Butler.