Oakland’s Mike Piazza might not get to cross the Bay Bridge for this year’s All-Star Game in San Francisco.

Not because of a bad season or even a recent collision with Boston’s Mike Lowell that landed him on the disabled list. Piazza might not go because he is listed as Oakland’s designated hitter and thus not included on this year’s All-Star ballot.

Frank Thomas, who hit 39 home runs and drove in 114 runs in Piazza’s role for the A’s last season, is now the Blue Jays’ designated hitter. He’s not on the ballot either. Neither is Jim Thome, who is hitting .340 and hit 42 home runs for the White Sox last season.

At a time when baseball would like to distract us from Barry Bonds and his pursuit of Henry Aaron’s home run record, baseball’s four-decade-long rules war (DH or no DH?) will likely make July’s All-Star Game as intriguing for who is not there as much as for who is there.

Why? Because San Francisco is a National League city, and the National League does not play with a designated hitter. The combination of a players vote and the preference of American League manager Jim Leyland may add one or two to the roster, but not all of the above will be going.

Thome can and has played first base for the Sox, but teams are allowed to list only one player at each infield position, and only three outfielders. Paul Konerko, the Sox regular first baseman, is on the ballot.

The Detroit Tigers may have signed Gary Sheffield to be their designated hitter in the offseason, but by listing him as a third outfielder, they bounced their everyday center fielder and leadoff man Curtis Granderson from the ballot.

Sheffield said recently he didn’t know that Granderson wasn’t on the ballot, and that he felt bad about it. But I can’t shake this sneaky feeling that an All-Star appearance was somehow worked into the two-year renegotiation of his contract upon arrival in Detroit.

It all seems so unnecessary and counter to what the event is supposed to be about – all-stars. Some hard-core National League fans would probably argue that fair is fair, and with homefield in the World Series determined by the result of this game, the National League should be able to play by its rules every other year.

But here’s a quick point: It is the third summer in the last four that the game is being held in a National League park. And the truth is, pitchers are routinely pinch-hit for in All-Star games, and often with sluggers.

You could make the case that because they must spend lavishly for the designated hitter, the American League has more quantity, if not quality, when it comes to sluggers. But again, should an All-Star Game emphasize equity over excellence? And even if one concedes a teeny advantage for the American League with the inclusion of the DH, does it justify the potential exclusion of some of the game’s stars – not to mention more recognizable and popular names like Thome and Piazza?