Now the Giants prospect is hoping the second one comes a little bit sooner.
Duffy went 3-for-5 with a grand slam and a career-high six RBIs on Wednesday night, leaidng the short-season Salem-Keizer Volcanoes to an 11-4 triumph over the Everett AquaSox.
Duffy singled and scored in the first inning before slugging a one-out slam on a first-pitch fastball from Victor Sanchez in the second.
"It was pretty cool. Coming around second base, I couldn't keep the smile off my face," said Duffy, who was homerless in 501 career at-bats at Long Beach State. "I kinda tried to keep my head down and keep a straight face, but when I looked up at my third base coach Hector Borg, I was grinning from ear to ear.
"It was definitely cool. I'm not a home run hitter, so anytime I do something like that, it's special for me. To do it as a grand slam -- I couldn't have have hit it any further -- was definitely a really good feeling."
The 21-year-old shortstop came up again with the bases loaded in the fourth and plated a run with a forceout. He singled up the middle to plate Ryan Jones in the sixth before flying out to end the eighth.
"I was on deck and there were runners on first and second with nobody out and I was like, 'You have to be kidding me. This could happen again,'" Duffy said of the potential for a second grand slam. "Kentrell Hill hit a ball to the wall and I thought it would plate a run, but the runners were looking to tag up and Hill stopped at first.
"Everybody in the stadium was like, 'Do it again'. It was exciting and pretty cool, but [Sanchez] threw me a couple off-speed pitches in that situation."
Selected in the 18th round of last month's Draft, Duffy entered Wednesday's game hitting .250 with two doubles and two RBIs in 28 Northwest League games. He identified two weaknesses in his game early in his Minor League career; one was his approach at the plate.
"In college, once you get runners in scoring position you get breaking balls and changeups to hit. But here, I'm looking for that off-speed pitch like in college, but they keep attacking you, whether there are runners in scoring position or not," he said. "They come at you with fastballs and they don't mess around. I need to learn that I won't get as many off-speed pitches.
"I haven't been hitting with runners in scoring position lately. The hitting coach [Ricky Ward] said I was trying to do too much and that I was focusing on the results rather than hitting something hard."
The second problem was mechanical. At Long Beach State, Duffy always used a leg kick as part of his timing at the plate. But when he struggled after returning from an injury, his coaches suggested he eliminate the extra movement to simplify his swing.
The California native took that kick-less approach with him to Salem-Keizer. On Wednesday, however, he decided it was time to go back to what always worked for him.
"It was best for me at the time, but I wasn't really excited about losing it," Duffy said. "Tonight I put in the leg kick that I had previously taken out and I was just feeling it. I was just focusing on putting the ball in play and getting it in the air.
"I just have to stay consistent because that will help me in the long run. If you have a good game, you want to have another one. If you lose your focus for one pitch, bam, error. Or you lose your focus at the plate and you take a fastball down the middle and it's the best pitch you see in the at-bat."
Volcanoes starter Raymundo Montero (3-3) gave up five hits and three walks over five scoreless innings. Ian Gardeck yielded four runs -- three earned -- on a pair of hits and three walks in the ninth.
Hill was 2-for-4 with a walk and a run scored, Joseph Rapp collected two hits and two RBIs and Sam Eberle was 2-for-4 with two runs scored and an RBI for Salem-Keizer.
Sanchez (4-1) was charged with seven runs -- six earned -- on six hits over four innings. He walked two and struck out two in suffering his first loss.