Giants fans could be seen showing their love for the catcher at Wednesday night's Warriors game in the form of the number 28 jersey some wore.
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"For me, it was a shocker today, even my daughters were like 'daddy, daddy, Posey's retiring? They were all shocked," said Giants fan David Castaneda.
Posey was more than just a baseball player to many that we spoke with, he was one of us.
"To be honest with you, he is like family," said Castaneda.
"He's an amazing player, I am 27 and I remember seeing that when I was in 8th grade, high school, and it kind of inspired me more to root for our local teams," said Giants fan Xavier Cortez.
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Posey will leave the major leagues after 12 years. Former big leaguer Bip Roberts says that Posey is up there with the best of the best to ever play the game.
"The thing I'm going to remember about Buster Posey is that he was cool under fire, he was always calm and cool," says Roberts who spoke about his time covering the Giants as a broadcaster in Posey's early years. "I would always, when he was in the box, hey what's going on Gerald? You know call him by his first name and he'd say, 'You dropped the Gerald on me', but I just enjoyed him!" says Roberts.
Fans tell us they'll remember two things. His resilience after that violent collision at the plate in 2011.
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"Sadly back then we thought he was done and he came back and gave us so many more years," says Giants fan Trish Herrera-Spencer.
And that certain Grand Slam back in the 2012 NLDS
"Game 5, Cincinnati, grand-slam off of Matt Latos," said one fan who continued saying, "It's pretty emotional for us San Francisco Giants fans. He's been here for 12 years. I think he's the heart and soul of the Giants and we're going to miss him."