The homer was just part of a huge day for Castro, who went 2-for-5 with six RBIs.
"It was a fun day," Castro said on Monday afternoon before the Marlins faced the Cubs at Wrigley Field. "I remember my first at-bat, I hit a homer. That's one of the things I'm never going to forget. Now, I'm here, back at Wrigley."
In 2010, Castro was a rookie from the Dominican Republic, who was called up from Double-A Tennessee. At the time, the infielder didn't speak much English, and he would do interviews in Spanish, assisted by an interpreter. Now, English doesn't give him any issues. He says watching television helped him learn the language.
On the day Castro made his MLB debut, everything was new to him, even how to get to and into the ballpark. Castro recalls having no idea how to get into the clubhouse at Cincinnati.
"I remember when I went to the ballpark, somebody had to tell me," Castro said.
With the Marlins and Cubs playing a three-game series, Castro returns to Chicago having recently hit his 100th big league home run, which came on Saturday, also at the Reds.
The Cubs dealt Castro to the Yankees after the 2015 season. Although he has since played at Wrigley Field, being in Chicago is special to the four-time All-Star. Miami acquired him in December as part of the Giancarlo Stanton trade.
"This is a great ballpark. I love it as a player," Castro said. "It's old, but you don't feel like it's old.
"I can always say they're the team that gave me the opportunity to be a professional baseball player and the opportunity to play in the big leagues."
On the Marlins, Castro is a veteran leader on a young squad.
"For us, he's been great," Marlins manager Don Mattingly said, "from the standpoint of leadership for our young players, his attitude and the way he goes about his business. He's always got a smile on his face. Solid with his work ethic and his approach. Really, when you have a young club, you need to have some older guys who have good solid approaches and daily routines."
Castro has accepted his role with a building team.
"We've got a lot of young players and players like I had when I was with the Cubs," Castro said. "I try to come in here every day and do my job. We've got a lot of guys who play hard, and we're coming to the ballpark every day to fight."
Worth noting On the injury front, right-hander Brett Graves (left oblique strain) is scheduled to throw a bullpen session on Tuesday at extended spring. Right-hander Elieser Hernandez (tooth infection) continues his rehab assignment with a start on Wednesday for Double-A Jacksonville. Chris O'Grady (left shoulder strain) continues his throwing program in Jupiter, Fla. Odrisamer Despaigne threw two innings and 30 pitches on Monday in an extended spring game.