Their line says, Bats: Both. Their lineage says a lot more.

The first great switch-hitter was shortstop George Davis, a Hall of Famer who drove in 136 runs in 1897. By 1927, 6.2% of all nonpitchers were switch-hitters. Frankie Frisch, a Hall of Fame second baseman for the Giants and Cardinals (1919-37), had a .316 lifetime average, the highest ever among switcheroos. But by 1952, the majors had only eight of them, 2.5% of all nonpitchers.

One, though, was a young Yankees outfielder -- a kid named Mickey Mantle -- and he single-handedly made batting from both sides popular again. "My father made me a switch-hitter when I was 11 because he loved Mantle," says Red Sox infielder Carlos Baerga. "I'm sure a lot of fathers did what mine did."

Most power-hitting switch-hitters -- Mantle, Eddie Murray, Reggie Smith, Lance Berkman (whose 94 extra-base hits last season were the most ever by a switch-hitter) -- were ambidextrous at an early age. Fast guys, on the other hand, usually switch later in life, sometimes as late as pro ball.

Cleveland's Omar Vizquel, a natural righthanded hitter, reluctantly became a switch-hitter when his former team, the Mariners, made him bat lefthanded. For the last five years, he has been a better hitter from the left side. Like Vizquel, most switch-hitters are natural righties who move to the other side of the box to 1) get a step closer to first base; 2) never have to see a breaking ball coming at them; and 3) avoid being platooned.

The number of switch-hitters in an era is tied to the style of game being played -- power or speed. Mantle had his share of followers, but his influence wasn't nearly as important as the onset of AstroTurf. The 1987 St. Louis Cardinals, who won the NL pennant under manager Whitey Herzog, regularly used six switch-hitters, beat the ball into the carpet and ran. By 1992, the major leagues had 99 switch-hitters, 17.2% of nonpitchers.

Today baseball is a power game again and the number of switch-hitters has dropped to 72, or 14.8%. Still, four of the six highest career batting averages among switch-hitters (minimum: 2,000 plate appearances) belong to active players: Chipper Jones (.307), Robbie Alomar (.306), Bernie Williams (.305) and Jose Vidro (.302). Switch-hitting will always give the batter an advantage, but it will remain a difficult thing to do well.

"I was so bad at first, I couldn't get the ball out of the infield," says Ray Durham of the White Sox. "I thought, 'There's no way it's ever going to work.' But after all the sweat, all the blood on my hands, now I'm actually better from the left side. I've even hit lefthanded twice against [lefthander] Andy Pettitte. How do you figure that?"

This article appears in the June 10 issue of ESPN The Magazine.