09/29/2012 11:42 EDT | Updated 11/29/2012 05:12 EST

Sounders clinch playoff berth, Whitecaps gain valuable point from 0-0 draw

VANCOUVER - Brad Knighton's long wait for another MLS shutout ended just in time to keep the Vancouver Whitecaps' playoff hopes alive.

Knighton picked up his first clean sheet in two years Saturday as the Caps drew 0-0 with the Seattle Sounders before a sellout crowd of 21,000 at B.C. Place Stadium.

"Obviously, it's been a long time coming," said Knighton, who had three saves on the night. "It's something I've been looking forward to."

Although the draw stretched Vancouver's winless streak to seven games, the Whitecaps (10-12-9) did gain a valuable point in their fight to hold on to the fifth and final playoff spot in the Western Conference. The Whitecaps maintained their two-point cushion on sixth-place Dallas, which tied with San Jose later Saturday.

The Sounders (13-7-10), meanwhile, clinched a post-season berth and can finish no worse than their current fourth-place standing in the West.

The shutout came after Knighton allowed late goals last weekend in a 2-2 home draw with Colorado and eight days earlier in a heart-breaking 1-0 road loss to Dallas.

"It's exciting, but I felt like we could have got three points," said Knighton. "We just got a little bit lucky there at the end."

Seattle goalkeeper Michael Gspurning recorded his sixth shutout of the season — but only after a wide-open Camilo missed a chance from close range in the game's dying seconds. His shot from the near post went just wide of the far post.

"The ball came to me, I just had to make time, but the shot (went) a little bit wide," said Camilo.

Gspurning preserved the draw as he stopped Vancouver captain Jay DeMerit in stoppage time.

"Obviously we’ve done a lot of work all season," said Seattle coach Sigi Schmid. "So it’s great to finally have that (playoff berth) officially secured, but our goal is still to get second place, so we’re disappointed in not getting three points today. (But) at the end of the game they had a fantastic chance with Camilo, so we can be fortunate that we didn’t walk out down."

Knighton's most important save came in the 88th minute as he dropped to block second-half subsitute Steve Zakuani's shot from about 20 yards out.

The Vancouver goalkeer also denied a dangerous Seattle chance early in the second half as he kicked out Eddie Johnson's from six yards in the 55th minute. Knighton also foiled Fredy Montero from 30 yards in the 28th minute and got help from Young-Pyo Lee in the 79th minute as the Whitecaps defender kicked a Jeff Parke volley off the goal-line.

"It was good to see him get the clean sheet," said Vancouver coach Martin Rennie. "I think he certainly deserved that."

But the Whitecaps' point came at a heavy price as they lost top scorer Darren Mattocks to a strained right hamstring in the first half. Mattocks said afterwards he will likely sit out Wednesday's home game against Chivas USA as a precaution, but hopes to return soon.

Mattocks left the game in the 38th minute after going down in Seattle's 18-yard box as Montero was slapping him and giving chase. The 22-year-old Jamaican's departure came after he went down in a heap and was helped off the field by a trainer. Camilo replaced Mattocks, setting the stage for his late miss.

Vancouver also lost midfielder John Thorrington to a left hamstring injury in the 17th minute. He was replaced by Matt Watson, who has played sparingly most of the season.

"Hopefully, (Mattocks and Thorrington's injuries are) not too serious. They were both playing well when they had to come off, while I also thought the guys who had to come on also did very well," said Rennie. "I think Matt Watson played his best game since he came to Vancouver (as a free agent in the off-season.)"

Mattocks and Kenny Miller started together at striker after coach Rennie said a day earlier he did not think they would start together. Rennie also made a notable change on the back line, inserting Andy O'Brien at central defender in place of Martin Bonjour.

"I thought collectively we did very well," said O'Brien. "We kept a clean sheet — and that's what defenders are for."

Both Vancouver and Dallas have three games remaining in which to secure a post-season berth.

Whitecaps captain DeMerit said the games can't come soon enough now that the club is regaining its form after going through many changes in mid-season as a result of signings and trades.

"For us to get a clean sheet against a Seattle team that scores a lot of goals (45 on the season) is a major step in the right direction," he said. "Obviously, (there is) some natural disappointment because we had chances to win the game. But they didn't fall for us tonight, so we've just got to keep going."

Notes: As a result of the draw, Portland won the Cascadia Cup, an in-season competition between Vancouver, Seattle and the Timbers. ... Television star Drew Carey — a Seattle minority owner — high-fived with fans. ... Vancouver midfielder Dane Richards served a one-game suspension for his eighth yellow card of the season. ... Whitecaps winger Omar Salgado (broken foot) did not dress. ... Sebastien Le Toux, who was traded to the New York Red Bulls in July, was mistakenly announced as a member of Vancouver's starting lineup instead of Miller. The mistake appeared to stem from the fact Miller inherited Le Toux's former No. 7 jersey.