This is the only change in baseball's playoff structure since the 1995 season, when wild-card teams were first added.

"This change increases the rewards of a division championship and allows two additional markets to experience playoff baseball each year," commissioner Bud Selig said in a statement.

Had there been additional wild-card teams last season, the Braves would have made the playoffs in the NL, while the Boston Red Sox would have qualified in the AL. Instead, each missed the postseason by a game, both going down with historic September swoons.

"I would've taken it last year," Braves manager Fredi Gonzalez joked Thursday.

At Red Sox camp Thursday, several players were wary of the change to the postseason.

"One game? That's kind of crazy," designated hitter David Ortiz said. "You know how many things we've got to move around and pack for one game? It'd make more sense for two wild cards to play at least a two-out-of-three series while the other teams take a break for three days because they won their divisions."

For the 2012 postseason, the five-game Division Series will begin with two home games for lower seeds, followed by home games for the higher seed. After that, it will return to the 2-2-1 format previously used.

"The players are eager to begin playing under this new format in 2012, and they look forward to moving to full realignment in 2013," MLBPA executive director Michael Weiner said.

As part of baseball's labor deal, the Houston Astros will switch to the American League for 2013, creating two 15-team leagues with three divisions each. Players wanted the change to equalize the chances for making the playoffs for every division.

Each season, eight of 30 major league teams have made the playoffs under the format that began in 1995, a year later than intended because of a strike that wiped out the end of the '94 season. The postseason included just the league winners from 1903-68, then increased to four teams in 1969 after the leagues split into divisions.

In the NFL, 12 of 32 teams make the playoffs. In both the NBA and NHL, 16 of 30 teams advance to the postseason.

Adding two more playoffs teams this year has been complicated because the regular-season schedule was drafted last spring and summer, and the extra game has to be put in place in a manner that doesn't disrupt the World Series schedule. In a further complication, both sides reached a consensus that ties for division titles would be broken on the field with a tiebreaker game under the new format, and not by head-to-head record.

Head-to-head record has been used since 1995 to determine first place if both teams are going to the postseason. But the sides decided that with the start of a one-game, winner-take-all wild-card round, the difference between first place and a wild-card berth is too important to decide with a formula and that a tiebreaker game should be played.

The Texas Rangers have won their division the last two seasons and advanced to the World Series. Still, they like the new plan.

"I think it's great," infielder Michael Young said. "Another team gets in the playoffs and it makes it so that winning the division matters more."

Rangers catcher Mike Napoli, noting that wild-card teams have fared well in the postseason of late -- the St. Louis Cardinals were a wild-card team and won the World Series over Texas last year -- said the new playoff format would give the division winners a little more of an advantage.

"That's the way it should be, I think," Napoli said. "You play 162 games with the goal in mind of winning the division. You want to make the playoffs and this gives another team a chance to do that, but the division is the big goal."

Information from ESPN The Magazine's Buster Olney, ESPN.com senior Jayson Stark, ESPNDallas.com's Richard Durrett, ESPNBoston.com's Rick Weber and The Associated Press was used in this report.