Back-to-back losses have stalled D.C. United's quest for a playoff spot.

Rebounding with another strong effort against the Vancouver Whitecaps can get United back on track, but the expansion Whitecaps have some unexpected momentum.

D.C. looks to avoid its first three-game slide in more than a year by completing a season sweep of Vancouver, with United set to make their first visit to BC Place Stadium on Wednesday night.

D.C. (9-10-11) is five points back of Houston and New York for the final two playoff spots in MLS. United have four games left, two more than the Dynamo and Red Bulls and one more than Portland, which is three points behind Houston and New York for a wild-card spot.

D.C. hosts the Timbers on Oct. 19.

United capped a 2-1-1 stretch with a 4-1 victory over Salt Lake on Sept. 24, appearing to signal that they are a serious contender to return to the playoffs for the first time since 2007. They failed to maintain that momentum, though, losing 3-2 at Philadelphia on Sept. 29 and falling 2-1 at Columbus three days later.

Now, D.C. is on the brink of its longest skid since dropping five in a row from July 15-Aug. 14, 2010.

"This is definitely the most important time of our season," captain Josh Wolff told the team's official website. "We know what's at stake over these next four games. We have to put everything together, and that starts on Wednesday in Vancouver."

United beat the league-worst Whitecaps (5-16-10) by a 4-0 score at home Aug. 13.

Dwayne De Rosario had two assists in that meeting, and his acquisition is a major reason D.C. is in the playoff race. The team acquired him from New York in July, and he's tied Charlie Davies for the team lead with 11 goals while adding seven assists in 15 games since.

De Rosario's impact has been evident over the past four contests, as he has scored five of United's nine goals while setting up two others.

Davies has found the net in one of the last 10 games, doing all the scoring in a 3-0 win over Chivas USA on Sept. 10.

The Whitecaps would like to damage United's playoff hopes and win consecutive games for the first time. They stunned playoff-bound Salt Lake 3-0 on Thursday, ending an 0-3-1 slide while handing Real a fourth straight defeat.

Camilo scored twice on penalty kicks Thursday, giving him a team-high 11 goals.

"For me, it's good (to lead the team in scoring), but (Eric Hassli) is the big player on this team," the 23-year-old Brazilian forward told the team's official website. "He supports us younger players and shows us everything - it's good for me."

Hassli, with 10 goals and two assists, will be available after serving a one-game suspension for an accumulation of yellow cards.