A day after he exited his final spring training game because of a stiff left shoulder, Duffy said he was ready to pitch Thursday at home against the Chicago White Sox.
"As of now, I feel good," Duffy said Sunday. "I don't really have too many comments. I feel good to go."
Duffy left in the third inning after throwing 32 pitches against an Arizona split squad. His first pitch bounced in front of the plate and his fastball velocity was 82 to 85 mph, about 10 miles less than his normal working velocity.
Duffy threw only 15 innings in spring training and no more than 4 1/3 innings in any start. He was 1-1 with an 8.40 ERA, allowing 14 earned runs and 19 hits, including four home runs. He walked nine and struck out 12.
"I'm feeling just fine this morning," Duffy said. "I knew what it was. It's just something we didn't want to push through. Initially, I tried to get my pitch count up. It just wasn't going to happen (Saturday). I wasn't going to go out there and throw with what I had. I knew coming into today that I'd be tested a little bit. We got the test done and everything was negative."
Duffy threw long toss of up to 100 feet and some changeups in a light session Sunday. He will throw a bullpen Monday in Omaha as a final test to get clearance for his second straight opening day start.
The 29-year-old had offseason elbow surgery after two stints on the disabled list last year with a strained right oblique and left elbow impingement.
The Royals have roster decisions to make on their bullpen, which manager Ned Yost said they would "have to take it right up to the end."
"Make sure Danny is OK, which I have a fairly high degree of confidence he is fine," Yost said. "It happened like two weeks ago (his shoulder tightened) and the next day he felt great. Fifteen minutes after he got in the clubhouse yesterday, he tested out perfectly. So I don't think it's going to be an issue. I think Danny is going to be fine."