NEW YORK-Andrew Miller knows how different the pennant races are this year.

“The Red Sox and the Yankees, you hear about them all the time,” the 21-year-old Detroit reliever said. “You didn’t hear about the Tigers a year ago.”

With a month to go in the regular season, the Tigers were on track for their first playoff appearance since 1987, but their AL Central lead was down to 41/2 games – less than half the 10-game bulge they opened on Aug. 8.

And while the AL playoff picture had come into focus, 11 of the 16 NL teams began Thursday within four games of a division or wild-card leader.

Why is virtually the entire NL still in it?

The three division leaders – Los Angeles, New York and St. Louis – are the only teams more than three games over .500.

“There’s a lot of parity throughout the league. It could be the effects of revenue sharing, in a way,” Dodgers general manager Ned Colletti said. “Teams have an opportunity to keep their better young players for a longer period of time.”

While San Diego, Philadelphia and Cincinnati are bunched at the top of the wild-card race, Arizona, Atlanta, Florida, Houston and San Francisco all are in position to make it to the postseason if they have good September runs.

Last year’s Padres set the record for poorest regular-season record of a postseason team at 82-80. While that mark appears safe, the worst record for a wild-card winner is in jeopardy; that mark is 77-67 by the Colorado Rockies during the strike year of 1995, according to the Elias Sports Bureau.

And the division leads of the Cardinals and Dodgers aren’t all that big. The New York Mets, with a huge margin in the East, are the only team whose postseason berth appears safe.

“The way the West is, every team is one good week from being in the running,” Giants reliever Mike Stanton said.

In the American League, the Yankees turned a four-game deficit into an eight-game lead as the Boston Red Sox plummeted due to poor pitching and health problems with David Ortiz, Manny Ramirez and Jason Varitek.

Detroit, baseball’s biggest surprise, won its first three games after the All-Star break and stood at 62-29. But the Tigers are 21-22 since then and have lost six of eight. “We have a good team,” said first-year manager Jim Leyland, credited for the transformation. “We’re not a fluke.”

St. Louis lost 14 of its first 22 games in August before rebuilding the lead back to 41/2 games. In contrast, the Marlins were 56-66 before a nine-game winning streak put them back in contention for the NL wild card.

Oakland, seeking its fourth AL West title, was just 45-43 at the All-Star break. The A’s finished August with nine straight wins to open a 71/2-game division lead, their largest since 1992.

Los Angeles sank to 47-55 after losing 13 of 14 following the All-Star break. But the Dodgers, at 71-62, lead the NL West by three games over the second-place Padres. The Dodgers went 21-7 in August.