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The downward spiral that is Stephen Strasburg takes center stage Thursday, as he looks to put a halt on his current winless streak when the Washington Nationals open a three-game series with the San Diego Padres.

Strasburg won his season debut April 1 versus Miami with seven shutout innings of three-hit ball. It appeared Strasburg was back on track after he was shut down at the end of 2012 and had to watch the playoffs from the dugout. Now it looks as if Strasburg could use a long siesta as evidenced by his 0-5 record and 3.61 earned run average in his last seven starts.

Washington is 1-6 in that stretch and dropped an 8-2 decision to the Chicago Cubs on Saturday in Strasburg's last start. The right-hander allowed four unearned runs and five hits in five innings to fall to 1-5 in eight outings to go along with a 3.10 ERA. Strasburg has pitched well in his starts, but just doesn't have the wins to show for it.

"It's frustrating. Stevie is throwing the ball well, he has a heck of a game going and it changed the momentum a little bit," said Nats third baseman Ryan Zimmerman, who didn't help the cause with throwing errors. "You feel bad. You don't want that to ever happen."

The Nationals have scored more than two runs just twice in Strasburg's appearances this season. He lost his only career start against San Diego last May 15 in a 6-1 loss, yielding four runs in four innings.

Edinson Volquez has been the opposite of Strasburg and is 3-0 with a 2.49 earned run average in his last four starts. The Padres are 3-1 in that time. Volquez did not record a decision in last Friday's 6-3 loss at Tampa Bay, but did pitch well and limited the Rays to a pair of runs in six innings.

"Volky hung in there ... it was a little maddening in that he was behind in the count a lot," Padres manager Bud Black said. "They didn't get many hits off him. They didn't hit many balls hard off him."

Volquez, a right-hander, started 0-3 in his first four outings -- all San Diego losses -- and is 1-1 with a 5.87 ERA in three career starts against the Nationals.

The Nationals have lost two straight and four of five games, and dropped the last two contests of a three-game set at Los Angeles.

In Wednesday's 3-1 loss, Dodgers starter Zack Greinke made an early return from a broken collarbone and held the Nationals to a run in 5 1/3 innings. Ross Detwiler drew the start for Washington and lasted only three innings, allowing two runs and six hits in a losing effort.

Detwiler was bothered by tightness in his lower back and was forced to leave the game. Nats catcher Wilson Ramos also departed the contest with a hamstring injury and is day-to-day.

"It's not all that great now. Hopefully, tomorrow morning it will feel a lot better," Detwiler said.

Adam LaRoche homered and Bryce Harper appeared in a pinch-hit role after missing Tuesday's game with side effects from running into the right-field wall Monday night. Harper is expected to be back in the starting lineup against the Padres.

The Nationals are currently on a 10-game road trip and will also visit San Francisco. They are still one game behind Atlanta for the NL East lead.

San Diego is only 4 1/2 games off the pace in the NL West and swept a two-game series from the Baltimore Orioles.

In an 8-4 win Wednesday at Camden Yards, Jason Marquis took the mound and fired five innings of two-run ball to improve to 5-2 on the season.

"They've got a great lineup, so you've got to make your pitches," Marquis said. "Some days you're not going to feel as good as others, but you've still got to make pitches in a big situation."

Alexi Amarista doubled twice and added a two-run homer and Everth Cabrera had four hits with an RBI for the Padres, who have posted back-to-back wins since losing three in a row and will play seven straight at Petco Park.

Kyle Blanks added a solo home run and John Baker drove in two for the Padres.

San Diego lost three of five matchups with Washington last season and have dropped six of the previous eight meetings between the clubs.