Music: {allcanada} WHITECAPS HOST SOUNDERS ON TSN2 WITH PLAYOFF SPOT ON LINE

VANCOUVER -- As first-half performances go, it was a thing of beauty.

Now, the question is: Can the Vancouver Whitecaps duplicate it at a critical time in their season?

The Caps were a dominant force in the opening 45 minutes when they last hosted the Seattle Sounders in May. With the teams set to meet again Saturday at B.C. Place, Caps coach Martin Rennie is looking for a similar effort as his team tries to retain its precarious hold on a Major League Soccer playoff berth.

"If we can have a similar performance to what we did the first time we played them here, we should have a good chance (to win)," he said after practice Friday. "To do that, we need to make sure we take our (scoring) chances."

You can watch the game live on TSN2 and TSN Mobile TV at 9pm et/6pm pt.

In May, the Whitecaps (10-12-8) built a 2-0 lead before the Sounders (13-7-9) rallied in the second half to forge a 2-2 tie. However, Vancouver has rarely played the same way since those first 45 minutes.

The Whitecaps had a firm grip on a playoff spot back then, but now hold just a two-point lead over FC Dallas in the race for the fifth and final playoff berth in the Western Conference. Dallas also plays Saturday, on the road against powerhouse San Jose, and is in position to overtake the Whitecaps.

Vancouver has gone winless in six games (0-5-1) while scoring just two goals in that span. Despite the difficult circumstances, Rennie is expecting a strong performance from his club, which usually plays well at home.

"A lot of players perform better under pressure," he said. "So I don't think that's a major issue."

Theoretically, the Whitecaps still have time to become the first Canadian MLS club to earn a playoff berth. But Rennie, often the epitome of a coach who stresses the positive, did not downplay the importance of Saturday's contest.

"It's a very key game," he said. "It's a chance we could have a really big swing in the points (in the standings) if we get a good result Saturday. So that's really what we're focused on and, of course, doing well and doing what we can to be the first Canadian team to ever make it to the playoffs.

"Any time you're playing in a big game against a (regional) rival, that's a chance to see who steps up and who takes over and who makes the most of the opportunity. Especially against a rival, it's even more important for us and more important for the fans than any other game. So it's a very key game -- and players need to step up."

As for which players can step up, Rennie was keeping his lineup to himself for fear of leaking any secrets to the opposition. But the coach said he will not start strikers Darren Mattocks and Kenny Miller together.

On Sunday, Miller came off the bench in the second half to score as the Whitecaps overcame a 1-0 deficit, took a 2-1 lead and then settled for a 2-2 tie with Colorado. He and Mattocks displayed some chemistry -- something that has been lacking among Vancouver forwards in a season that has witnessed several roster changes through signings and trades.

"I think we'll go with a slightly different shape," said Rennie, declining to elaborate.

Whatever the formation, Mattocks is expected to take on much of the scoring responsibility. The 23-year-old Jamaican rookie hopes to repeat the strong showing he delivered in the May meeting between the Vancouver and Seattle, when he made his first MLS start.

Mattocks said the Whitecaps were a different team then, noting many Vancouver players who toiled in that game are gone. But the newcomers, as demonstrated against Colorado, are starting to show cohesion with the holdovers at long last.

"Now, the team is finally starting to come together," he said. "That first half (in May) is what we're looking for come (Saturday.)"

Mattocks is also seeking his first goal since he scored in a 2-1 road loss to Real Salt Lake on July 27. The two-month dry spell is deceptive, because Mattocks has missed games to suspension and Jamaican national team duty and been deployed as a substitute -- but he is hungry to score again.

"As a striker, that's really frustrating now, but I never let that get to me," he said of his lack of goals. "The most important thing is that I just keep working hard. Honestly, as long as my is getting (results), if I don't score, that's fine. But as a striker, putting the ball in back of our net, that's our job."

The Whitecaps are 0-1-1 against Seattle this season and 0-2-2 since entering MLS in 2011. Despite the strong first game, the Caps put in a poor effort in a 2-0 loss in the Emerald City in August.

Vancouver captain Jay DeMerit said his club has to use the strong first half in May as a confidence boost and make sure it plays well in the "final third" of the pitch by finishing off scoring chance up front or "locking the door" at the back.

If the Whitecaps can do that, he contended, they can duplicate their strong first-half showing against Seattle in May -- and earn more points to reduce the pressure they face qualifying for the playoffs.

But with the Whitecaps and Dallas having four games left in the regular season, Vancouver is running out of time to ease its burden.

"Every game, as far as we're concerned, is a playoff-type calibre now as we finish the season," he said.