SANDY, UTAH – Mario Martinez got his first start in Major League Soccer on Thursday, and he made it count.

After another 81 minutes of scoreless soccer between Sounders FC and Real Salt Lake, Martinez sizzled a low line drive past goalkeeper Nick Rimando and into the net.

Nine tense minutes of regulation and five frenzied minutes of stoppage time later, Seattle celebrated the first playoff win in its four-season MLS existence.

“It’s a monkey off the back,” midfielder Brad Evans said. “I think everybody feels that way. We played our hearts out in the game.”

The result propels the Sounders to the Western Conference final against the Los Angeles Galaxy. The first match is 6 p.m. Sunday in Carson, Calif. The concluding game of the aggregate-score series is 6 p.m. Nov. 18 at CenturyLink Field.

“We’ll get ready for that,” coach Sigi Schmid said. “L.A. thought they were playing Salt Lake: They put out a press release that said they were playing Salt Lake. So we hate to disappoint them. That’s motivation enough for us right now. ... We know what’s at stake.”

Heading into the Western Conference quarterfinal finale Thursday, neither the Sounders nor RSL had scored in the last 309 minutes of the series, counting back to May – and the Sounders hadn’t scored on RSL since the 2011 playoffs.

The resolution match at Rio Tinton Stadium began like more of the same. Both teams had chances, and both teams watched them produce nothing on the scoreboard.

That is, until the 81st minute – with extra time and perhaps penalty kicks looming. Fredy Montero sent a pass to Martinez just inside the left side of the penalty area that he lasered inside the far post.

“I’m happy so much because the team actually got the win tonight,” Martinez said through a translator. “... It was a great opportunity on the personal side for me ... to defend the colors of the team.”

Martinez got his chance due to the unavailability of club assists-leader Mauro Rosales, who was held out with a hamstring injury.

“(We knew Martinez) had close to 90 minutes in him,” Schmid said. “... We also knew that his passing could help us. We felt that his ability in set pieces – we wanted to hit some swinging corners – could help us as well. Obviously, he delivered for us with a great goal.”

Martinez had made only three regular season appearances, in part because he had joined the Sounders at midseason and in part because of time away with the Honduras national team.

His frustration boiled over last month with a Twitter post indicating he would rather play for another team.

However, that outburst was a distant memory Thursday, as he relived his game-winner while happy music poured from the visitor’s locker room.

“It was always in my mind that I would get my chance,” Martinez said. “And it got here at the most important time, the playoffs. I gave everything for the team and for the people that brought me here and had confidence in me.”

The Sounders defended that slim lead to the final whistle.

RSL pushed forward for cross after cross, corner after corner and chance after chance through those final minutes.

The home team ended up outshooting Seattle, 14-9, and putting nine on target to the Sounders’ five. But nothing got past goalkeeper Michael Gspurning.

“It really comes down to a pretty simple game; if you don’t score goals you’re never going to win games,” RSL coach Jason Kreis said. “You have got to win to advance.”

With the final whistle, the Sounders ended both a tense 190-minute series and a three-season run of playoff frustration.

“I’m just so happy for our fans, the players, the coaches,” general manager Adrian Hanauer said. “I know it’s trite and everybody says it, but just everybody who puts energy in. I’m even happy for you guys. Just a fantastic team effort and a moment of brilliance.”