(AP) -- Tony Gwynn, the Hall of Famer with a sweet left-handed swing who spent his entire 20-year career with the Padres and was one of San Diego's most beloved athletes, died of cancer Monday. He was 54.

Gwynn, nicknamed "Mr. Padre," had been on a medical leave since late March from his job as baseball coach at San Diego State, his alma mater. He died at a hospital in suburban Poway, agent John Boggs said.

"For more than 30 years, Tony Gwynn was a source of universal goodwill in the national pastime, and he will be deeply missed by the many people he touched," Commissioner Bud Selig said.

Gwynn had two operations for cancer in his right cheek between August 2010 and February 2012. The second surgery was complicated, with surgeons removing a facial nerve because it was intertwined with a tumor inside his right cheek. They grafted a nerve from Gwynn's neck to help him eventually regain facial movement.

Gwynn had said he believed the cancer was from chewing tobacco.

San Francisco Giants third base coach Tim Flannery played a long time with Gwynn and then coached him. Flannery says he'll "remember the cackle to his laugh. He was always laughing, always talking, always happy."

"The baseball world is going to miss one of the greats, and the world itself is going to miss one of the great men of mankind," Flannery said. "He cared so much for other people. He had a work ethic unlike anybody else, and had a childlike demeanor of playing the game just because he loved it so much."

In a rarity in pro sports, Gwynn played his whole career with the Padres, choosing to stay rather than leaving for bigger paychecks elsewhere. His terrific hand-eye coordination made him one of the game's greatest contact hitters. He had 3,141 hits, a career .338 average and won eight NL batting titles. He excelled at hitting singles the other way, through the "5.5 hole" between third base and shortstop.

Gwynn played in the Padres' only two World Series and was a 15-time All-Star.

He homered off the facade at Yankee Stadium off San Diego native David Wells in Game 1 of the 1998 World Series and scored the winning run in the 1994 All-Star Game. He was hitting .394 when a players' strike ended the 1994 season, denying him a shot at becoming the first player to hit .400 since San Diego native Ted Williams hit .406 in 1941.

Gwynn befriended Williams and the two loved to talk about hitting. Gwynn steadied Williams when he threw out the ceremonial first pitch before the 1999 All-Star Game at Boston's Fenway Park.

Gwynn retired after the 2001 season. He and Cal Ripken Jr. -- who spent his entire career with the Baltimore Orioles -- were inducted into the Hall of Fame in the class of 2007.

Gwynn was a two-sport star at San Diego State in the late 1970s-early 1980s, playing point guard for the basketball team -- he still holds the game, season and career record for assists -- and outfielder for the baseball team.

Gwynn always wanted to play in the NBA, until realizing during his final year at San Diego State that baseball would be the ticket to the pros.

"I had no idea that all the things in my career were going to happen," he said shortly before being inducted into the Hall of Fame along with Ripken in 2007. "I sure didn't see it. I just know the good Lord blessed me with ability, blessed me with good eyesight and a good pair of hands, and then I worked at the rest."

He was a third-round draft pick of the Padres in 1981.

After spending parts of just two seasons in the minor leagues, he made his big league debut on July 19, 1982. Gwynn had two hits that night, including a double, against the Philadelphia Phillies. After doubling, Pete Rose, who had been trailing the play, said to Gwynn: "Hey, kid, what are you trying to do, catch me in one night?"

Survivors include his wife, Alicia, daughter Anisha and son Tony Jr., who plays with the Philadelphia Phillies.

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AP Sports Writer Janie McCauley contributed to this report.