Leiman, a catcher, summed up his experience with just one word.
Leiman is eligible to compete at the Pitch, Hit & Run National Final at Citi Field in Flushing, N.Y., prior to the All-Star Home Run Derby on July 15.
All 30 MLB ballparks host a regional championship that determines first-place boys and girls winners in four separate age groups, ranging from 7-14. If Leiman's score ranks among the top three nationally in the Boys 9-10 age group, he'll earn his first trip to New York.
The 24 national finalists will be announced on June 30 on MLB Network.
"I'm very proud," said Bryan Leiman, Ryan's father. "It's beyond words to see him to do that. I knew he could do it. It was just a matter of getting it done. He's worked hard to get here."
Marlins manager Mike Redmond appeared briefly following the competition, taking a few pictures with the participants. Brantly also took a couple of photos with the kids.
While Redmond never competed in a contest like MLB Pitch, Hit & Run when he was younger, he reflected on his first experience at a Major League ballpark.
Growing up in Washington, Redmond attended Mariners games on little league days at the Kingdome in Seattle.
"[We would] get to see the turf -- all that stuff," Redmond said. "Back in the day, to me, that was the best stadium I had ever been in in my life. That's just the way I grew up. That's all I knew."
Brantly's first time on the field at a Major League stadium did not come until his junior year of high school, when he tried out for an Angels scouting team at Angel Stadium of Anaheim.
However, the Miami catcher said he identified with the kids competing at Marlins Park on Saturday.
"I wanted to be in the big leagues when I was five," Brantly said. "Anything else was just practice for me in my head. I was like, 'I'm ready to go with the big leaguers.'"