SEATTLE -- It's been 15 years since Ken Griffey Jr. made what he thought was a small statement in support of Jackie Robinson, flip-flopping his familiar No. 24 jersey to bear Robinson's number 42 for one game.

That was April 15, 1997. And Griffey, well aware of Robinson's impact on the game, asked the Mariners' equipment managers to fix him a new jersey on the 50th anniversary of Robinson breaking baseball's color barrier.

Never in his wildest dreams would Griffey, who retired in 2010, have imagined every player, coach and manager throughout the Major Leagues wearing No. 42 at the same time, as now happens throughout baseball on Jackie Robinson Day each April 15.

At the time, the Mariners center fielder was responding to a request from the Jackie Robinson Foundation. Robinson's widow, Rachel Robinson, gave her permission, and Griffey gladly complied for what everyone figured was a one-game salute.

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But the idea stuck with Griffey, who learned Negro League history and Robinson's story from his father, Ken Griffey Sr., while growing up in Ohio.

Griffey knew what Robinson meant to the game, to his dad and to all who followed. So it was that 10 years after his initial 42 tribute, now with the Reds, Junior made an important phone call. Commissioner Bud Selig had by then retired Robinson's number throughout baseball, but Griffey wanted to wear it once again in 2007, on the 60th anniversary of Robinson's arrival in the Majors.

"It was a Sunday night call, I remember," Selig said last October while presenting Griffey with the Commissioner's Historic Achievement Award during the World Series. "I was just walking in the house, my phone was ringing. Ken called me, and it was his idea to wear No. 42 as a tribute to Jackie Robinson on the day commemorating his historic achievement.

"He asked my permission to do that, and I, of course, granted it. It told me a lot, however, about Ken, about how much he understood the history, how much he understood the impact of Jackie Robinson. So I've often gotten credit for something, but really he made a phone call to me on a Sunday night at home that I'll never forget.

"And with Ken leading the way, it began to catch on with other players. Eventually it led to all on-field personnel throughout baseball wearing No. 42 on Jackie Robinson Day, a tradition that continues to this day and will continue at least as long as I'm around."

Griffey was back with the Mariners in 2009 when Selig made the move to have every player wear No. 42 on April 15.

"It was just my way of saying thank you, my way of giving back," Griffey said of his idea at that time. "I had no idea it would turn into something like this."

But he's thrilled that it did, knowing what it meant to so many people who'd gone before him. It turns out, young Griffey was, indeed, listening when his dad talked to him about Robinson and introduced him to former Negro League players as a child.

"Joe Black, Brooks Lawrence, Chuck Harmon Sr., all were good friends with my dad," he said. "They figured I should know a little about baseball history, or just history itself. They proceeded to drill me on certain things.

"Then, getting to play in pro ball, I had a guy named Willie Mays pull me aside every year. They didn't tell you like they were drilling it into your head. It was more them telling stories, like a grandfather would tell their grandson. That's how I learned about certain things."

And at the forefront of it all was Robinson, the player who opened the door for all that has happened since. Griffey didn't forget, and his simple move on April 15, 1997, to wear that No. 42 jersey for the Mariners led to the entire Major Leagues doing the same thing now.

For Griffey, the inspiration was simple.

"It's just the things that he did," Griffey said when he was presented with the Commissioner's Award. "I mean, if he didn't play, you never know how long it's going to take for another African-American to play, and would my dad have played, and would I have the love for the game if my dad didn't play?

"So he was the start of it all, for not just African-Americans, but everybody else to play. It was my way of respecting him for what he did, for him wearing that uniform allowed me to wear my uniform, and you have to give thanks in a certain way. It was my way of saying thank you to him for allowing that to happen."