WASHINGTON -- Stephen Strasburg wouldn't admit his poorest outing this season gave him added motivation. His teammates saw something extra in his dominating performance Sunday.
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"He came out a little angry," Washington's Jayson Werth said. "I think he acted like he had something to prove today, and he pitched really good. I like that Stras."
Strasburg (12-5) struck out six and walked one, extending his scoreless streak against the Marlins to 27 innings and lowering his ERA to 2.97 in 127 1/3 innings.
"He's a way better pitcher. Before he was a thrower," Miami manager Ozzie Guillen said. "He's matured. He's better."
In his previous start, Tuesday against Philadelphia, Strasburg tied his career high by giving up six runs. Strasburg has allowed four runs or more four times this season and in his next starts has gone 4-0 and allowed just two earned runs.
"I'm still learning how to pitch and call a game and really pick up on little things that happen in the game that you can use to your advantage," Strasburg said. "Today was a big step forward for me in that process, but there's still a long way to go."
The right-hander is pitching his first full major league season following reconstructive elbow surgery in 2010. Washington officials say they plan to end his season early, and he is thought to have a limit of about 160 innings, although the Nationals have not been specific.
Strasburg's strong day extended from the mound to the plate. In the second inning he came up with runners on second and third and one out, and hit a two-run single to right field. He's batting .343 (12 for 35) with seven RBI.
"Someone said, 'When we shut him down, can we keep his bat? Can we use him as a pinch hitter?' " Nationals manager Davey Johnson said with a smile. "Highly unlikely."
Strasburg gave up a double to Scott Cousins in the first inning, then retired his next nine batters. He never allowed more than one runner in an inning.
"He was great. That was back to the old Stras," Adam LaRoche said. "There was something about when he came to the dugout before the game. We could all sense a different attitude today. I don't know if it was something to prove to himself, that he still had it or to be able bounce back from the last one -- whatever it was, he had a little fire in his belly."
LaRoche was 2 for 3 with his own two-run single in the second inning as the Nationals won three of four from Miami and maintained a three-game lead over second-place Atlanta in the NL East. LaRoche is hitting .442 with seven home runs and 16 RBI in his last 14 games.
Drew Storen pitched a one-hit ninth for his first save since Sept. 28. It was the first save chance for Storen since he returned July 19 from right elbow surgery.
"That was a lot of fun," Storen said. "Especially when you're pitching for a first-place team in that situation, it doesn't get much better than that."
Miami's Jose Reyes hit a fourth-inning single that extended his hitting streak to 24 games, the longest in the majors this season. Reyes starts a series Tuesday at his former team, the New York Mets.
Ricky Nolasco (8-11) gave up four runs, eight hits and four walks in six innings. He is 0-5 with a 7.16 ERA in his past five starts, allowing at least four runs in each.
Miami scored in the seventh when Carlos Lee and Greg Dobbs led off with back-to-back doubles against Craig Stammen. The double gave Lee an 11-game hitting streak, the 19th time in his career he has hit safely in at least 10 consecutive games.
- Nationals LF Michael Morse singled in the fifth inning to extend his hitting streak to 14 games, the longest for the Nationals this season.
- After striking out swinging in the fourth inning, Harper slammed his bat on the plate, breaking it in half. Miami catcher John Buck said Harper apologized during his next at-bat. "I told him, 'Don't worry about it. I did the same thing when I was your age. It was a metal bat, and I was in high school,' " Buck said. "It's a learning experience in front of the eyes of the whole country and the world. I bet you he won't do that any more -- at least in the next couple of weeks."
- The Nationals start a 10-game trip Monday at Houston. Washington has the best road record (33-21) in the majors.