Baltimore's Ryan Flaherty struck out with the bases loaded in the ninth inning to halt the Orioles' late-inning magic as they lost 2-1 to Boston on Sunday to remain a game behind New York in the tight American League East race.
Baltimore had rallied on Saturday for their 16th straight extra inning victory, but their latest charge fell just short and they missed a chance to catch the first-place Yankees, who lost to Oakland.
The defeat snapped Baltimore's (87-65) six-game win streak.
New York (88-64) was beaten 5-4 by the Athletics, ending the Yankees' run of seven consecutive wins but they remained a game in front of Baltimore with 10 contests to play in the regular season.
With the A's and Yankees tied at 4-4 in the sixth, Oakland's Cliff Pennington hit a go-ahead RBI single and the visiting Athletics held on for the victory.
Oakland (86-66) now leads for the second American League wild card spot by three games.
The Detroit Tigers (80-71) lost the opener of a doubleheader against Minnesota 10-4 to fall a full game behind the Chicago White Sox in the American League Central race.
Detroit's Miguel Cabrera collected his Major League-leading 132nd run batted in as he pursues baseball's elusive triple crown. He leads the league in batting average and runs batted in and is tied for the top spot in home runs.
In the National League, Atlanta beat Philadelphia 2-1 as they stretched their hold on the top wild card spot.
The San Francisco Giants clinched their second NL West Division title in three years on Saturday night with an 8-4 victory over the San Diego Padres.
The Giants, winners of the 2010 World Series, claimed the pennant despite losing All-Star closer Brian Wilson to a season-ending injury and leading hitter Melky Cabrera to a 50-game doping suspension.
(Writing by Jahmal Corner in Los Angeles; Editing by Gene Cherry)