During his 12-year career, Sean Casey’s most endearing trait became his most enduring.

Fellow major leaguers dubbed him ‘‘The Mayor’’ because he seemed to know everyone he met. He chatted up runners at first base, making the game’s luminaries smile by respectfully calling them ‘‘Mr.’’ before offering a compliment.

When he retired on Tuesday to move into broadcasting — a career that fits his gift for gab — the 34-year-old Casey remained proud of his reputation as baseball’s Mr. Congeniality.

‘‘It means a lot to me if I’m looked at as a good guy in the game and a pretty good player,’’ said Casey, who is joining the fledgling MLB Network as a studio analyst. ‘‘It’s a nice combination.’’

It got him a lot farther than he ever expected.

Casey made three All-Star teams with Cincinnati, had a sensational World Series with Detroit in 2006, finished with a .302 career batting average and experienced every moment with a boyhood wonder that charmed fans and fellow players alike.

Those moments still make him marvel.

‘‘When I homered off Jeff Suppan in Game 4 (of the ’06 Series), it took me back to being that 12-year-old little kid in the backyard,’’ Casey said on a conference call Tuesday. ‘‘I remember rounding first base thinking, ’I just homered in the World Series!’’’

Whether he was in a World Series or signing autographs after a spring training game, he still felt like a fan.

Part of it was Casey’s personality, and part of it was his less-than-balleyhood background. As a high school player in Pittsburgh, the plodding infielder couldn’t even get a college to consider him. When they saw that 7.5-second time in the 60-yard dash, they turned away.

‘‘I wasn’t the five-tool guy, the guy you looked at and said, ’This guy is going to be the next big guy,’’’ Casey said. ‘‘I had no scholarship offers coming out of high school. I always felt I could hit and was going to make myself a great defensive player. I always believed I was going to play in the big leagues. I don’t think a lot of other people did.’’

He played at the University of Richmond, developing into one of the country’s most consistent hitters. The Cleveland Indians gave him a chance, then traded him to the Reds on the eve of the 1998 season opener for pitcher Dave Burba, who was Cincinnati’s top starter.

Then, another stunning twist. Two games into the ’98 season, Casey was hit on the right side of the face by a thrown ball during batting practice. He broke bones around the eye socket and needed surgery. There were doubts about whether he would ever be able to see clearly out of the eye.

He recovered, and his career took off. When he made his first All-Star game in 1999 at Fenway Park, he had teammate Barry Larkin videotape his lone at-bat from the dugout, a moment shown on national television.

Casey played for the Reds through 2005 and got the first hit in Pittsburgh’s new ballpark, one of his proudest moments. He got to play for the Pirates in 2006, then moved to Detroit and had perhaps his finest moments in his only World Series. He batted .529 in five games with two homers, two doubles and five RBIs as the Tigers lost to the Cardinals.

He hit .322 in 69 games for Boston last season with no homers and 17 RBIs. Rather than play in a limited role again this season, he accepted the offer to join the MLB Network, which started this month.

‘‘Sean is considered one of the most popular players to play the game in the last 15-20 years,’’ said Tony Petitti, the network’s president. ‘‘That will give us added access.’’

The move gives Casey a chance to spend more time with his wife and three children. It also gives him a chance to keep chatting away about the latest play.

‘‘Throughout my career, everyone was always interested in what I was talking about at first base and everything like that,’’ Casey said. ‘‘Now people can see me talk on TV instead of wondering what I’m saying at first base.’’