BRYCE HARPER showed why his manager put him in the No. 3 spot for his fifth career game.

The 19-year-old phenom hit a tiebreaking RBI double in the sixth inning, lifting the Washington Nationals to a 2-1 victory over the visiting Arizona Diamondbacks on Thursday night.

Ross Detwiler (3-1) did his part as well. The lefthander allowed one run and three hits over 6 1/3 innings in his longest outing this season. He retired the first eight batters he faced and didn't allow a hit until the fifth inning.

Ian Kennedy (3-1) lost for the first time in 13 starts, snapping a personal nine-game win streak.

The NL East-leading Nationals took two of three from Arizona and have won five of their six series this season.

Washington manager Davey Johnson moved Harper up four spots in the lineup a day after he went 3-for-4 with two doubles, and the rookie delivered. He is now 6-for-6 in his five games, with four doubles and three RBI.

Asked about the move before the game, Johnson said, "I mean, he's swinging the bat good. He's had quality at-bats. It's what you do. I don't care if his name's Harper or whatever. Or how old he is. "He looks like a pretty good choice to me."

Harper also had an interesting night on the basepaths.

He hit a weak grounder back to Kennedy in the first, but the pitcher's throw was wide and the No. 1 overall pick in the 2010 amateur draft took second on what appeared to be an error.

The Diamondbacks decided to appeal and Harper was called out for failing to touch first base.

In other games * 

At St. Louis, Erik Bedard struck out a season-high 11, including seven straight batters, and Pedro Alvarez hit a go-ahead home run as the Pittsburgh Pirates beat the Cardinals, 6-3, to avoid a three-game sweep.

Bedard (2-4) was pulled after five innings. Alvarez hit his two-run drive in the sixth.

* At San Francisco, Hanley Ramirez drove in a pair of runs without a hit to back Anibal Sanchez' first win in four starts, and the Miami Marlins defeated the Giants, 3-2, to complete a three-game sweep.

Sanchez (2-0) allowed one run on seven hits, struck out five and walked one in seven innings.

Before the game, the Giants learned that slugger Pablo Sandoval has a broken hamate bone in his left hand that will require surgery. He is expected to miss 4 to 6 weeks. He had the same injury last year, but on the other hand.

* At Cincinnati, Scott Rolen hit a sacrifice fly in the 10th inning as the Reds defeated the Chicago Cubs, 4-3, for a two-game split.