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Gene J. Puskar, Associated Press
Atlanta Braves' Chipper Jones acknowledges fans as he heads for the locker room following a 4-0 win over the Pittsburgh Pirates in the final game of the regular baseball season in Pittsburgh, Wednesday, Oct. 3, 2012.

A dropped fly ball by Josh Hamilton, a home run by Ryan Zimmerman and pitch by pitch, the baseball playoff picture became a bit more clear on the final day of the regular season.

The Oakland Athletics clinched the AL West on Wednesday, trumping Texas 12-5 by taking advantage of Hamilton's error. The New York Yankees later hoped to claim the AL East crown, owning a one-game edge over the Baltimore Orioles.

Zimmerman and the Washington Nationals got sized for hats with postseason patches, then beat Philadelphia 5-1 to earn home-field advantage all the way through November, if necessary.

The playoffs begin Friday when the defending World Series champion St. Louis Cardinals visit Chipper Jones and the Atlanta Braves in the winner-take-all NL wild-card matchup. On Saturday night, Cincinnati will be San Francisco in Game 1 of the division series.

The rest of the postseason pairings were still to be determined.