ST. PETERSBURG, Fla. - With Gary Sheffield and Mariano Rivera healthy again, the New York Yankees look even more formidable in their quest for the best record in the American League and homefield advantage in the playoffs.

A “nervous” Sheffield returned to the lineup for the first time since May 29 and made an impressive debut at first base Friday night. The ever steady Rivera earned his 34th save in his first appearance since Aug. 31, helping the AL East champions beat the Tampa Bay Devil Rays 4-1.

“I’m treating this like the World Series right now because I’ve got to be ready when it comes to the playoffs,” Sheffield said, conceding he had some anxious moments in his first game at a new position.

“He was nervous,” shortstop Derek Jeter said of the longtime outfielder. “He said he doesn’t remember being that nervous before.”

Rivera, meanwhile, shrugged off some initial rust and struck out the side around a broken-bat single and a hit batter in the ninth.

“I was anxious. I couldn’t wait to pitch,” said Rivera, sidelined with a strained right forearm. “I’m happy I went in there and finished the way I wanted.”

Sheffield, who had seven putouts, saved a run with the score tied 1-1 by scooping third baseman Miguel Cairo’s low throw out of the dirt to end the sixth with a runner on third. He also handled a low throw from Jeter in the fourth.

“It looked like he had been there a lot longer than just working out this past week,” Yankees manager Joe Torre said.

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“I thought he reacted real well to when the ball was hit. That’s what you really have to get used to. When you’re playing third or playing short or the outfield and the ball is hit to somebody, you watch it unless it’s hit to you. But as a first baseman, when the ball is hit you’ve got to go to the bag. He didn’t have any trouble reacting to that.”

The nine-time All-Star went 0-for-3 before leaving the game after the Yankees took a three-run lead in the seventh.

“Sheff is a good athlete, that’s the thing. He came up as a shortstop. He played some third,” Jeter said. “Footwork, knowing where to be, that will take a while for him to get used to.”