NEW YORK -- Replay ball!

Umpires will be allowed to check video on home run calls starting Thursday after Major League Baseball, guardian of America's most traditional sport, reversed its decades-long opposition to instant replay.

"Like everything else in life, there are times that you have to make an adjustment," baseball commissioner Bud Selig said following Tuesday's announcement. "My opposition to unlimited instant replay is still very much in play. I really think that the game has prospered for well over a century now doing things the way we did it."

The 74-year-old Selig, who described himself as "old fashioned" and an admirer of baseball's "human element," softened his opposition following a rash of blown calls this year.

For now, video will be used only on so-called "boundary calls," such as determining whether fly balls went over the fence, whether potential home runs were fair or foul and whether there was fan interference on potential home runs.

"Any time you try to change something in baseball, it's both emotional and difficult," Selig said. "There's been some concern that, well, if you start here, look what it's going to lead to. Not as long as I'm the commissioner."

Replay will go into use with three series scheduled to open Thursday: Philadelphia at the Chicago Cubs, Minnesota at Oakland and Texas at the Los Angeles Angels. For other games, replays will be available to umpires starting Friday.