Yet, on Saturday night, there was the left-handed Duffy mowing down the Baltimore Orioles with precision and looking as if he might throw the first perfect game in the franchise's history.
Finally, with two outs in the Orioles' seventh, Adam Jones grounded a sharp single into center field and the perfect game and the no-hitter were over in one deflating moment.
Even so, Duffy and the Royals -- with closer Greg Holland surviving a harrowing ninth inning -- got a 1-0 victory after losing two straight to the Orioles at Kauffman Stadium.
In his seven-plus shutout innings, Duffy gave up two hits, walked none and struck out two. He used 97 pitches. But when asked what was working for him, Duffy pointed to his teammates.
"My defense -- my defense played a great game," Duffy said. "A lot of hard-hit shots at the boys and they stayed right in there. Gordo [Alex Gordon] made a spectacular play in left and I just tried to execute and do my best to get outs, and it clicked tonight."
Jones' hit came on a 1-0 count on Duffy's 83rd pitch of the game. The lefty kept his composure and got the third out as Chris Davis popped out. The 24,064 fans gave Duffy a standing ovation as he walked to the Royals' dugout.
When Nelson Cruz grounded a single to left field to start the eighth, manager Ned Yost brought in right-hander Wade Davis to relieve Duffy. The 25-year-old Californian got another standing O and waved and doffed his cap to the crowd as he walked off the field.
"Duff had it all going -- he was ahead in the count, he was throwing strikes with all his pitches, he was some kind of special," Yost said.
"He dealt. He was on a roll," Jones said. "There were some balls hit hard off him, but right at guys. He threw strikes and pounded the zone. He made us swing the bats."
Duffy's efficiency came while working with backup catcher Brett Hayes, who was giving regular Salvador Perez a night off.
"We were on the attack all day and Hayes called a great game," Duffy said.
The Royals got the only run off Bud Norris in the first inning as Nori Aoki singled to left field, stole second base and sped home on Billy Butler's single to center. The hit snapped an 0-for-10 skid for Butler.
"Anytime you get two-out RBIs and two-out knocks, those are hard to come by," Butler said. "Those are pressure situations. ... The ones with two outs seem to spark you."
Nick Markakis grounded out on Duffy's first pitch of the game and quickly a pattern was established. Three up, three down. Duffy got help from Alcides Escobar for the third out of the fourth as the shortstop glided behind second base for Jones' grounder and, twisting, threw him out.
In the sixth, Caleb Joseph hit a wicked line drive that third baseman Mike Moustakas speared.
"It was a little above my head to the left, but I was in good position. Dale [Sveum, infield coach] put me over there in a good spot," Moustakas said.
And in the Royals' dugout: silence about the possible perfecto.
"When those things are going on, you act like nothing's going on -- it's a normal game," Butler said. "You definitely don't want to say, 'Hey, they haven't had a baserunner.' You don't say things like that because baseball players are superstitious."
As the seventh began and the Orioles' batters began to get their third look at Duffy, Markakis hit a fly ball toward the left-field corner, but Gold Glover Gordon was ready.
"Before that even happened, I was thinking that if it's even close, I'm diving for it. So that's what happened," Gordon said. "Markakis sprays the ball good that way. He's a good opposite-field hitter so when he came up, I knew there was a possibility, and I think he had two strikes on him, so I was on my toes ready to go."
Gordon raced over, dived and caught the ball in fair territory, skidding through the warning track in foul ground as he clutched his prize.
"I saw it off the bat and I was like, 'Gordo's got a bead on that, he's going to get that," Duffy said. "No worries, I don't even have to look."
Machado gazed at strike three, just Duffy's second strikeout, and then Jones hit a solid grounder past the mound. Duffy knew it was a hit.
"Yeah, he hit it hard and it was right up the middle," Duffy said. "Esky's the best defensive shortstop in the game, in my opinion, and if anybody could get that, it's him. And it was just a hard shot."
But it was still 1-0 and the bullpen had work to do. Wade Davis took over and got the next three batters, two on strikeouts.
Holland had to work through a tense ninth inning in which the Orioles loaded the bases with two outs. But the game ended as Cruz struck out.
"Wade came out and was nails and Greg has ice in his veins. He's a stud," Duffy said.
So, evidently, is Duffy. This was just his third start in place of Chen, but he's looking pretty secure in the rotation after this performance.
"I'm happy with this outing but you can't be satisfied in May," Duffy said. "We're looking at the big picture and I'm happy that everything clicked tonight. It's huge for my confidence, but it's a long road ahead and we've got to play four more months to get into the postseason, and that's what I'm focused on right now."