NEW YORK >> With less than a month to go before opening day, baseball at last decided who’s in and who’s out come October.

Now, even a third-place team can win the World Series.

Major League Baseball made it official today, expanding the playoff format to 10 teams by adding a wild-card club to each league.

"I hope we get that extra spot," said new Houston Astros general manager Jeff Luhnow, whose team is coming off a 56-106 finish that was the worst in the majors. "I think it’s great any time you have more markets involved."

Who knows, maybe a rookie such as Bryce Harper will get that shot this year.

"Cool," the 19-year-old Washington sensation said after a game against college kids. "It’s great. Hopefully, we’re that playoff team."

Boston and Atlanta sure could’ve used this setup last year. They went through awful collapses in September that eventually cost them playoff spots on the final day of the season.

"I think the more, the merrier," new Red Sox manager Bobby Valentine said. "I think for the fans, the players, the energy at the end of the season, I don’t mind. What would it be, a third of the teams? I think it’ll be good."

This is the first switch in MLB’s postseason format since the 1995 season, when wild cards were first added. The move creates a new one-game, wild-card round in the AL and NL between the teams with the best records who are not division winners.

"It’s a good thing for baseball. That seems to be what the people want," Detroit manager Jim Leyland said.

"There are a lot of mixed emotions but as long as the playoffs don’t get watered down, it’s fine, but that won’t happen in baseball," he said.

The additions mean 10 of the 30 MLB teams will get into the playoffs. That’s still fewer than in the other pro leagues — 12 of 32 make it in the NFL, and 16 of 30 advance in the NBA and NHL.

The long-expected decision was announced less than an hour before Seattle and Oakland started the exhibition season. On March 28, the Mariners and Athletics will play the big league opener in Tokyo.

"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.

Also, a tweak: 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.

MLB said that with schedules already drawn for this season, the postseason had to be compressed to fit in the extra games. Hence, fewer off-days for travel.

"I don’t think it really changes the way you look at this season. You really have to fight to win your division," New York Yankees manager Joe Girardi said. "It is kind of strange to start on the road. That doesn’t quite seem right, but it’s a one-year thing. I understand why they’re doing it."

If the World Series goes to Game 7 this year — as it did last season, when the wild-card St. Louis Cardinals won the championship — it would be played Nov. 1.

"I like the extra playoff spot. I like the one-game playoff because it really gives the advantages to the division winner," Los Angeles Dodgers manager Don Mattingly said this week.

As in, it’ll be real dicey for the wild-card contenders to immediately jump into a winner-take-all game, then quickly turn around to start the division series.

Starting this year, too, there’s no restriction on teams from the same division meeting in that best-of-five division series.

Baseball players’ union head Michael Weiner said there had been internal discussions way back about possibly having six playoff teams from each league. He said that once bargaining began with owners on a new labor deal, it was clear MLB only wanted five.

"The players were in favor of expanding the playoffs," Weiner said.

In particular, he said, the players wanted to put more emphasis on winning a division, especially when MLB goes to a pair of 15-team leagues next year with three divisions each. The Astros are switching from the NL to the AL to make that possible.

A portion of the money generated by the one-game playoffs will go in the players’ pool that is split among the postseason participants.

In 1999, Valentine and the New York Mets won a one-game tiebreaker for the NL wild-card spot.

"I didn’t think that entering the playoffs in ’99 when I had to play a one-game playoff against Cincinnati that the next round was cheapened," he said. "It seems to be similar to that. I don’t know if it’s the same thing, but it seems."

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AP Sports Writer Jimmy Golen and AP freelance writers Mark Didtler, Carl Kotalo, Maureen Mullen and Jeff Berlinicke contributed to this report.