"It's definitely a representation of the courage that he had to do what he did. Without him, it affects everybody in this clubhouse -- not just the African-Americans," Harrison said. "We wouldn't be playing with those guys if he didn't have the courage he did. It's definitely representative of his courage, and to take a day out to recognize him is special."
This is Harrison's sixth season in the Majors, and he appreciates the significance of April 15 each year. It was Opening Day in 1947, the day Robinson broke baseball's color barrier and became the first African-American to play in the Majors.
While Robinson's story is familiar to most, Harrison said it is still important to remember his legacy and pass it on to the next generation of players and fans.
"You don't want to lose the history of the game. There's going to be people every year you've got to teach the history," Harrison said. "There are guys playing T-ball right now that need to understand the history. Somebody may find out something and say, 'I never knew that about Jackie Robinson.' It's good to have it."
Along with wearing Robinson's No. 42, some players further honor the occasion with special cleats, socks or accessories. Does Harrison have anything planned?
"I've got something up my sleeve," he said, smiling. "You'll see it tomorrow."
Adam Berry is a reporter for MLB.com. Follow him on Twitter at @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.