And then he'll just sit down.
It hasn't happened yet, though. Each of the three homers hit since his big league debut Friday has been followed by a curtain call.
"It's a crazy experience," said the 27-year-old rookie. "You kind of get frozen in the moment."
His dad and brother thought it was pretty neat, too. They watched it from the visitor's clubhouse at Turner Field in Atlanta. Dave Duncan is the Cardinals' pitching coach. His son, Shelley's brother Chris, plays for St. Louis.
"He's really good," said Chris, who is about two years younger. "He's always been really good. He just needed an opportunity."
Duncan, who actually shares his father's first name but goes by his middle name, was taken in the second round of the 2001 draft after playing college ball at Arizona. He rattled around the Yankees' system for six years until he was called up on Friday.
"This is more than you expect but I think Shelley put in his time and he's done his work. I expected he would go up there and be able to compete," Dave Duncan said. "He's having a lot of success right now. He's developed enough that he should be able to compete on a daily basis."
Among the position players who made it to the majors sooner are Philadelphia slugger Ryan Howard and Jonny Gomes of the Devil Rays.
While some of his contemporaries excelled, Duncan kept plugging away in the bushes. He was leading the Triple-A International League in slugging at .577 and had 25 homers for Scranton/Wilkes-Barre when he was called up.
On Saturday, in the opener of a day-night doubleheader, Duncan hit his first major league homer to cap a five-run sixth inning during a 7-3 win. Sunday, Duncan hit a three-run homer that gave the Yankees a 13-3 lead and got him cheered out of the dugout yet again.
"It's great to see this kid who's been working five or six years in the minor leagues," manager Joe Torre said. "He certainly has caught everyone's attention."