BALTIMORE -- For one miserable night, the New York Yankees reverted to the form they displayed over the first two weeks of the season.
It was a step back they could ill afford in the middle of a tight pennant race.
"Sometimes these things get away from you, and you can't do a whole lot about it," Yankees manager Joe Torre said.
New York's third loss in 16 games, combined with Boston's split of a day-night doubleheader with Toronto, left the Yankees and Red Sox tied atop the AL East. Both teams have five games left, meaning the division title will be decided when the front-runners meet this weekend for a three-game series at Fenway Park to close the regular season.
The Red Sox and Yankees are also tied with Cleveland atop the wild-card standings.
New York lost five of six to Baltimore over a 10-game span in April, but recovered in time to make a playoff run. The Yankees had won seven in a row over the Orioles until getting blown out in this one.
The Yankees trailed 5-1 before Sheffield hit a two-run homer in the third inning. He put New York ahead with his 11th career grand slam, a shot to left in the fourth that made it 7-5.
"He had two great swings and got us the lead. He gave us a chance," said starter Mike Mussina, who didn't get out of the second inning. "It just was not a good night to be a pitcher."
An RBI single by Miguel Tejada and Jay Gibbons' two-run homer off Al Leiter (4-5) in the fourth put Baltimore back in front, and the Orioles scored five runs off three relievers in the fifth to make it 13-7.
Javy Lopez led off with his 13th homer, and first since Aug. 25. After a walk and two singles loaded the bases, a passed ball let in a run and Felix Rodriguez issued back-to-back walks to force in a run. Wayne Franklin then walked in a run and gave up a sacrifice fly to B.J. Surhoff.
Mora drove in five runs and scored four, Gibbons went 3-for-4 with a walk and four RBI, and rookie Bernie Castro had three hits and scored four runs to help the Orioles end their longest skid of the season.
"I think this game made us realize we still have some good players, and if we play like we're able to play, then we can compete a little better than we've been," interim manager Sam Perlozzo said.
When Sheffield hit his slam, however, the Orioles couldn't help believing that this game might be like all the rest during their horrid losing streak.
"It's hard not to think here we go again. It's been that kind of stretch for us," Gibbons said.
It was the first time since Aug. 5 -- and only the second time since June 4 -- that Baltimore reached double figures in runs.
Aaron Rakers (1-0) pitched 2 1/3 scoreless innings to earn his first major-league win.
Sheffield's two homers gave him 33 for the year, and in the seventh he hit a shot to the left-field wall that was caught by a leaping David Newhan.
Derek Jeter hit his 18th homer for New York, and Bernie Williams hit two singles to pass Joe DiMaggio for fourth place on the Yankees' career hit list. With 2,215 hits, Williams trails only Lou Gehrig, Babe Ruth and Mickey Mantle.
Making his second start since missing three weeks with an elbow injury, Mussina gave up five runs and seven hits in 1 2/3 innings. It was his shortest outing since July 1995, when he recorded only two outs while pitching for Baltimore against Kansas City.
The bullpen didn't fare much better.
"Not one thing I did tonight (worked)," Torre said. "I never picked the right guy out of the bullpen."
Jeter started the Yankees off by hitting Bruce Chen's second pitch over the center-field wall, his fifth leadoff homer of the season and 17th of his career.
The Orioles answered with two runs in the bottom half. After Castro doubled and went to third on a single by Tejada, Gibbons doubled in a run and Surhoff hit a run-scoring groundout.
Baltimore chased Mussina during a three-run second that made it 5-1. After Mora hit a two-run double and Tejada followed with an RBI single, a single by Gibbons ended Mussina's night after 50 pitches.
- New York needs one homer to match the fourth-highest total in franchise history (223).
- Sheffield is 10-for-24 with 10 homers and 14 RBI lifetime against Chen.
- It was the most runs New York scored in a loss since an 11-10 defeat in Boston on July 24, 2004.