Buster Posey, the 2013 NL MVP, is scheduled to become a free agent after the 2016 season. (Ezra Shaw/Getty Images)

The Giants have quietly begun talks with All-Star catcher Buster Posey on a “mega-deal” contract extension, according to a CBSSports.com report.

Jon Heyman reports word of a “decent-sized gap” between the Giants and Posey in early contract talks, but the difference is not insurmountable.

Posey, the reigning National League Most Valuable Player, has been a big part of the Giants’ two World Series wins in the last three years. The fact that he’s 25 years old could lead Posey to seek a deal of 10 years or longer, according to Heyman.

Giants chairman Larry Baer acknowledged last week that the team and its franchise player were already discussing a deal that would cover three extra arbitration years on Posey’s current contract. He is scheduled to be paid $8 million in 2013 and becomes a free agent after the 2016 season.

Posey, who had the major league’s best batting average (.336) to go with 24 home runs and 103 RBI in 2012, already owns the MLB record for largest first-year arbitration settlement at $8 million for 2013.

Buster Posey was named 2012 National League Most Valuable Player. (Ezra Shaw/Getty Images)

The Baseball Writers Association of America named Buster Posey the 2012 National League Most Valuable Player.

Posey led the National League in hitting at .336, while also hitting 24 home runs with 103 RBI and a .957 OPS.

He was considered the favorite to win the award.

San Francisco Giants catcher Buster Posey is recovering from the extensive left leg injuries that sidelined him last season, but he’s not quite 100 percent. Posey won’t play in Saturday’s Cactus League opener against the Arizona Diamondbacks — manager Bruce Bochy tells MLB.com that Posey is “two, three, maybe four days” away.

Posey must first pass two baserunning tests — sliding and rounding the bag — before the Giants will allow him to appear in an exhibition game.

“He’s not quite ready, but he’s real close,” Bochy said.

“I’d say that’s very accurate,” added Posey. “I’m feeling great, and everything’s going well. We’re just kind of sticking to the course, and I don’t think it’ll be long before I get in some games here.”

Posey won National League Rookie of the Year honors when he hit .305 with 18 homers for the world champion Giants. His 2011 season ended on May 25 in a gruesome collision at home plate with Marlins outfielder Scott Cousins.