SAN DIEGO -- Clutch hits have been few and far between for the San Diego Padres this season.

Mark Kotsay delivered a big one Thursday night.

Kotsay's pinch-hit double off All-Star reliever Tyler Clippard in the eighth inning drove in two runs and lifted San Diego to a 2-1 victory against the Washington Nationals.

"We talked about what a difference one hit would make in a lot of games and tonight you saw it," Padres manager Bud Black said. "We had some opportunites in the game and we didn't get that hit until then."

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With the Padres trailing 1-0, Orlando Hudson drew a one-out walk and Cameron Maybin dropped down a bunt single against Clippard (1-2). Kotsay followed with a double to right-center to put San Diego ahead.

"Mark is a veteran and an experienced hitter -- one who had a good at-bat against a very talented relief pitcher," Black said.

Andrew Cashner (1-1) pitched a perfect eighth and Huston Street earned his second save. Three pitchers combined on a four-hitter for San Diego, which improved to 6-14 and averted a three-game sweep.

The NL East-leading Nationals (14-5) had won four straight and eight of 10. The franchise was looking for its first sweep in San Diego since the Montreal Expos accomplished the feat in July 1994.

Kotsay pinch-hit against Clippard in the seventh inning Tuesday night with runners on second and third and one out in a 2-1 game. Kotsay saw 12 pitches in that at-bat and fouled off seven before finally popping out.

"I missed a few pitches I felt I could have put in play Tuesday," Kotsay said. "Even though it was a great at-bat from the perspective that I battled, I was still disappointed with the result. Tonight I got ahead in the count and I told myself to get my sights up because he throws a lot of fastballs up."

Clippard wasn't happy with the way he went after Kotsay.

"I kind of had a mental lapse out there tonight," the right-hander said. "On Tuesday, I got him out on changeups and I felt he might be sitting on that pitch tonight. I more or less second-guessed myself and threw him four fastballs after getting behind in the count.

"I've said all along I need to stick to my strengths to be successful," Clippard added. "It was just poorly executed and the pitching selection wasn't good, either. It was kind of frustrating on my part."

Jayson Werth's home run with one out in the seventh off Padres starter Edinson Volquez snapped a scoreless tie. It was Werth's second of the season.

The Padres, who left 11 runners on base, had starter Edwin Jackson in trouble in the fourth when Nick Hundley singled and Yonder Alonso doubled to open the inning. But Jackson struck out Hudson before an intentional walk to Maybin. The right-hander then struck out Jason Bartlett and got Volquez to ground out.

In the sixth, Hudson tripled with two outs but was stranded when Jackson got Maybin to ground out to first baseman Adam LaRoche, who flipped the ball with his glove to Jackson for the out at first.

"I got some timely strikeouts and they made some great plays behind me," Jackson said.

In the seventh, the Padres loaded the bases with two outs, but Clippard struck out Hundley to end the inning.

Jackson allowed six hits in 6 2/3 shutout innings. He struck out six and walked three. Nationals pitchers have eight scoreless starts in 19 games this season.

Volquez went seven innings, giving up a run and three hits while walking one and striking out seven.

Notes

• Nationals manager Davey Johnson said 3B Ryan Zimmerman will see a doctor in Los Angeles on Friday to have his ailing right shoulder examined. Johnson said Zimmerman, out since last Saturday, was "not able to swing the bat" Thursday and would be examined and perhaps receive treatment. Johnson said a determination on whether Zimmerman will go on the disabled list would be made after his visit with the doctor. An MRI showed no structural damage.
• The Padres called up RHP Dale Thayer to replace RHP Micah Owings, who was placed on the 15-day DL.
• Washington LHP Ross Detwiler (2-0, 0.56 ERA) will open the series at Dodger Stadium on Friday night against LHP Clayton Kershaw (1-0, 1.66).
• San Diego LHP Cory Luebke (2-1, 2.56) will open a three-game series Friday night at San Francisco.