"It's an honor to be on the same field as these guys," Chapman said. "I'm just going to soak it all in and enjoy it."
After meeting Josh Donaldson, Craig Gentry and Yoenis Cespedes, Chapman fielded ground balls and took batting practice, launching several balls over the 388-foot marker in left-center field.
"It still doesn't even seem real," Chapman said. "My dream was to always play professional baseball. Having never been drafted out of high school, today my dream's coming true."
Chapman plans to head to the club's Spring Training complex in Arizona on Tuesday before joining Oakland's Class A affiliate in Beloit.
Despite boasting a 95 mph arm off the mound, Chapman has no plans of becoming a pitcher.
"I told them that I can move around and play all three spots in the infield, so I'm ready to play wherever they want me to, but I'm assuming it'll be third base," said Chapman.
"I want to play every day, that's for sure."
Chapman was with his mom, dad and sister on Monday -- and with his agent, Scott Boras, who watched his client take grounders from the A's dugout.
"He's got a big, big arm," Boras said. "It'll be one of the best throwing arms in the Major Leagues. His glove is Gold-Glove caliber."
The 21-year-old Chapman, who named Donaldson and Dustin Pedroia as two players he admires, simply enjoyed putting on the uniform.
"I wore white cleats in high school," Chapman said, "so it's pretty normal, I guess."