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WASHINGTON (Reuters) - Jason Marquis outduelled Tim Lincecum to pitch the Washington Nationals to a 3-0 win over the San Francisco Giants at Nationals Park on Friday.

Marquis pitched a complete game, allowing just five hits with seven strikeouts and not issuing a walk.

"I never worry about the opposing pitcher other than when I step in the box," Marquis said.

Laynce Nix hit a two-run home run in the second inning to drive in Wilson Ramos. In the fifth inning Ian Desmond scored from second on a single by Marquis, who drove a chin-high fastball into the outfield to aid his cause.

Lincecum nearly matched Marquis, allowing three runs on seven hits while striking out seven in seven innings without allowing a walk but was left ruing his knee-high changeup to Nix.

"I should have known better with a low-ball hitter," Lincecum said. "I should have buried it."

(Reporting by Mike Mouat in Windsor, Ontario. Editing by Nick Mulvenney)