Published: Sep 21, 2012 12:46 AM EDT
Updated: Sep 21, 2012 6:33 AM EDT

WASHINGTON (AP) - While the Washington Nationals wrapped up a playoff spot Thursday night, the Los Angeles Dodgers' chances of making the postseason took a hit.

The Dodgers fell 4-1 at the NL East leaders for their 10th loss in the last 14 games, and manager Don Mattingly acknowledged a playoff slot may be slipping away.

"You know, honestly, it does. It feels like it is a little bit, and I don't think there's any way for us to look at it other than that," he said. "I mean, it's, yeah, we're going the wrong direction."

Los Angeles (77-73) is three back of St. Louis for the NL's second wild-card spot. Milwaukee moved ahead of the Dodgers with its win over Pittsburgh.

"For us at this point, we're going to have to put a run together that's going to be more than just win a series," Mattingly said.

The Dodgers trail NL West-leading San Francisco by 10 games. On Aug. 19, they led the division by a half-game. They're 10-18 since.

"There's been urgency for the last three weeks to a month, it seems like," Mark Ellis said. "First we were chasing the Giants, and now we're chasing the Cardinals. There's been urgency for a long time."

Los Angeles managed just four hits, including Ellis' fourth-inning home run.

In the Dodgers' last 10 games, they've been shut out twice and held to one run three times.

"It's always frustrating when you can't figure out how to score runs," Matt Kemp said.

"I'm not going to give you a different answer. We haven't been able to score runs. One run is not going to win games. It's that plain and simple."

Ross Detwiler's six strong innings and Ryan Zimmerman's RBI double keyed the Nationals' big win.

Washington's magic number to win the NL East was reduced to eight. The Nationals lead idle Atlanta by 5½ games.

The Nationals became the second team in the majors to clinch a playoff spot this year. Cincinnati sealed its slot earlier in the day.

Los Angeles hasn't been in the postseason in three years, and hasn't played in the World Series since 1988.

"We've theorized this thing to death at this point. I wish I had the answer to what, what's going on. I really can't say that I do have an answer," Mattingly said.

"Are we trying to too hard? Yeah, I do think that we are sometimes. Is that the reason that we've kind of struggled for a long period of time? I'm not sure that's the only reason."

Detwiler (10-6) allowed just Ellis' homer and two singles. He struck five and walked one. Drew Storen pitched the ninth for his third save.

Zimmerman's third-inning double scored Bryce Harper with Washington's first run. Zimmerman took third on an infield out and scored on a wild pitch by Chris Capuano (11-11).

The Nationals added two runs in the fourth on a walk to Ian Desmond, an RBI double by Danny Espinosa and a sacrifice fly by Kurt Suzuki.

Capuano allowed four runs, three earned, and six hits in five innings.

"It's winning time right now, and when there's a lot of teams in the mix for one spot, you know, you've got to get hot," Capuano said.

NOTES: Mattingly said that LHP Clayton Kershaw was continuing with his throwing program. Kershaw will have to demonstrate he's free from pain in his right hip before he'll be able to pitch again, the manager said. ... Mattingly said RHP Chad Billingsley (right elbow) will begin to throw on Friday in Cincinnati. Billingsley, who hasn't pitched in more than two months, isn't close to returning. ... Dodgers RHP Kenley Jansen appeared in his first game since Aug. 27. Jansen, out with an irregular heartbeat, retired the only batter he faced. ... Los Angeles will start RHP Aaron Harang on three days' rest on Sunday. ... RHP Joe Blanton (9-13, 4.97 ERA) will start for Los Angeles against Reds RHP Bronson Arroyo (12-8, 3.74 ERA) on Friday night.