SEATTLE -- Ken Griffey Jr. knew he was going to be elected to the National Baseball Hall of Fame on Wednesday, but the honors kept coming when Junior got a call from Mariners president Kevin Mather the following day letting him know his number 24 is going to be retired at Safeco Field on Aug. 6.

"They said, 'We've got a little surprise for you,'" Griffey recalled on Friday after a news conference at Safeco. "'We're going to put your name up next to Jackie Robinson's.' And that's when things hit. That definitely caps a long, wonderful week."

Griffey will become the first Mariner to have his number retired and it means even more to him that he'll join Robinson, whose No. 42 hangs in every ballpark in the Major Leagues. Griffey is the one who first asked former Commissioner Bud Selig if he could wear Robinson's 42 on Jackie Robinson Day, a tradition now upheld by every player and coach in MLB each year.

"If [Robinson] didn't do what he did, maybe none of this would be possible," Griffey said. "Maybe baseball wouldn't be the same. We'd still have divided Negro Leagues to baseball. Now I've got great friends who are from Japan to Australia, guys I get a chance to play with and meet and I call and text when they do great things. If [Robinson] didn't do what he did, who knows if any of this is happening?

"Having my number next to him, I don't think I did half of what he did. Baseball-wise, yeah, you're going to look at numbers and things like that. But the way he went about his life and things he did off the field, nobody can compare to that. "

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Ken Griffey Jr. Weekend in Seattle will take place during the Aug. 5-7 series against the Angels, two weeks after the Hall of Fame induction in Cooperstown. The Aug. 5 game will be a Griffey bobblehead night, Aug. 6 will be the pregame jersey retirement ceremony and Aug. 7 will be a Griffey replica-jersey day for the first 20,000 fans. His number also will be retired throughout the club's entire Minor League system.

"Ken Griffey Jr. was the first player selected in the 1987 Draft, a first-ballot Hall of Famer, the first player in Hall of Fame history to amass over 99 percent of the vote and the first player to wear a Mariners cap on his Hall of Fame plaque," Mather said. "It seems only fitting that he be the first Mariners player to have his number retired."

The club also announced Griffey will be at Safeco Field to throw the ceremonial first pitch for the team's home opener on April 8.

Single-game tickets go on sale March 5, with a special presale for Mariners Mail subscribers (mariners.com/mail) on March 1.

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"It means a lot," Griffey said. "Anytime somebody does something for you, you can't take it for granted. The writers voting, the Mariners not telling me until the last moment they were going to do this, it means a lot.

"We play to go win games and have fun and be competitive and not embarrass ourselves. For them to say, we don't want anybody to wear this number, it's overwhelming and scary. But it's one of those things that makes you feel good as a person and player that they respected what you did."

Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB, read his Mariners Musings blog, and listen to his podcast.