San Diego Padres legend Tony Gwynn died at age 54 on Monday.

He had been undergoing treatment for cancer and had been on medical leave from his job coaching San Diego State since April.

Gwynn retired in 2001. He played for 20 seasons, compiling more than 3,000 hits and entering the Hall of Fame in 2007. His incredible stats show he was one of the best hitters in the history of the sport.

According to CSN Philly, Gwynn was first diagnosed with cancer in 2010. He has had two surgeries, one to remove a tumor on his cheek.

His son, Philadelphia Phillies player Tony Jr., told CSN on Sunday, "This has been the hardest of the four years he’s fought it, by far."

Major League Baseball announced the news.

We mourn the passing of Hall of Famer and @Padres icon Tony Gwynn, who died today at the age of 54. pic.twitter.com/lXPEVSzRj3 — MLB (@MLB) June 16, 2014

Gwynn was the rare superstar athletes who played his entire career for a single team. In his Hall of Fame speech, he had some great things to say about the organization:

"I played for one organization, the San Diego Padres, and when this day started out today, I thought I was going to go third. I thought I was going to get to hear what other people said about their towns and their cities. I only know one way, that's the Padre way. I wore brown, I wore the brown and gold, I wore the blue and orange. I didn't get a chance to wear the sand and whatever color blue you want to call that, but I'm proud as heck to be a San Diego Padre. I played for one team, I played in one town. I told the people of San Diego when I left to come to Cooperstown, they were going to be standing up here with me, so I hope they are just as nervous as I am, because this is a tremendous honor to be here today."

He was one of the best ever.