Justin, the Freeport, Long Island native, was hinting at the future from an early age.
On Sunday, Dunn, the 19th pick in the first round of the 2016 MLB Draft by the New York Mets, made his home debut for the Brooklyn Cyclones, pitching in front of his mom, his dad, Ed Dunn, and more than 20 members of his family.
"Basically my entire family was here today at the game," Dunn said. "So it was good to pitch in front of them. A lot of people haven't seen me pitch since I was young, so for them to be here for my first win at home was awesome."
Dunn's parents were in attendance for his last outing for Boston College on June 10 in the NCAA Super Regionals against Miami, but the two had not seen him pitch in New York since he was in high school.
"It was a surreal moment," Ed said. "Ever since he was 7 years old, this is where he wanted to go and try to make it to that next level. Just to see him get that opportunity today is a very surreal moment. I'm very happy for him."
The 6-foot-2 right-handed pitcher threw two scoreless innings and picked up a 4-3 victory over the Hudson Valley Renegades. He came into the game in the seventh inning with the score tied at 3, but a Nick Sergakis home run in the seventh gave Brooklyn the lead for good.
Dunn threw his three breaking pitches -- changeup, curveball and slider -- and maxed out at 97 mph with his fastball.
"His stuff is reminiscent of a young Doc Gooden," Cyclones manager Tom Gamboa said. "He's not as tall as Doc, but he's real fun to watch."
Dunn got into some trouble in the eighth after hitting the first batter in the inning and then walking another one. But he and the Cyclones were in for some magic, as Renegades third baseman Jim Haley popped into a 2-6-3 triple play.
"Never, and I've never seen one done that way either," Dunn said when asked if he'd ever been involved in a triple play.
The Cyclones will be conservative with Dunn, who logged 65 2/3 innings with Boston College this season. He started eight games for the Eagles in 2016, and the Mets plan on using him as a starter. But in the meantime, Dunn will come out of the bullpen, pitching every six days for two-inning stints.
"I'm not looking into it too much," Dunn said about coming out of the bullpen. "Whenever I get a chance to get the ball, it's just work for me, getting better every day."
And Dunn will count on the support of his family, which -- with just a 30-minute drive to Brooklyn in the way -- plans on attending every home game for the Cyclones.
"He was only home a minute, and we only got to see him a minute," Donna said. "So now it's like, we can breathe and check in with him, make sure all is well."
After two outings with the Cyclones, all has gone well for Dunn. He has thrown four scoreless innings and has struck out three batters.
Perhaps the only adjustment Dunn has had to make as a professional so far has been accepting the fact that he can no longer root for the Yankees, his and his family's favorite team.
"Did I envision him pitching in New York? Yes," Ed said. "Of course, I always thought he'd be pitching in the navy and white, but this is a great organization, a pitching-rich organization, and I'm just happy to see him somewhere that he's going to be able to progress and hopefully make it to his dream."