SAN FRANCISCO (KGO) -- Buster Posey is the greatest catcher in Giants history, but his legacy goes beyond baseball.
"I think we were among if not the first nonprofit he got involved with. I like to think that we helped shape his family's philanthropy," said Ken Sommer, Director of Advancement at George Mark Children's House.
In 2014, Buster Posey and his wife Kristen visited the George Mark Children's House. A pediatric palliative care center. There he met one of the patients, Justin.
"They basically sat and talked baseball. Justin wasn't a patient he was a baseball fan and it was wonderful for him to have that opportunity," said Sommer.
Two years later, the Posey's launched the BP28 foundation focused on pediatric cancer research.
"If it's not in the millions it's in the high hundreds of thousands of children that Buster has supported," said Lauren Franklin, Community and Volunteer Liaison with UCSF Benioff Children's Hospital.
One of the factors that moved the Poseys was learning that only about four percent of cancer funds raised in the U.S go to pediatric research.
His foundation has raised over $5.5 million and created partnerships with multiple cancer research institutions, including UCSF's Benioff Children's Hospital.
Luz Pena: "How often does he come to the hospital?"
Lauren Franklin: "At minimum 5 times a year."
Franking hopes that Posey's retirement gives him more time to visit children at UCSF Benioff Hospital.
Sommer believes Posey's meeting with their patient Justin helped his recovery.
"He is 25. We haven't seen him here for few years, but I spoke to his mother a little bit ago and he is actually doing really well," said Sommer.