SEATTLE — The Colorado Rapids slid by the Sounders in two early-season matches, and went about its way the rest of the Major League Soccer season.

Six months later, the two teams met up again — in a first-leg match of the Western Conference finals.

Only this time around, the Sounders had a shiny, new weapon to unleash on what was seemingly an impenetrable defense, considered the best in MLS.

His name is Nicolas Lodeiro.

And once again, Seattle’s electric midfielder put his beautiful herky-jerky, one-cut-and go movements on display.

Lodeiro’s penalty kick in the 61st minute was the game-winning goal, and the Sounders grabbed the advantage over Colorado with a 2-1 victory Tuesday night in front of 42,774 at CenturyLink Field.

The second leg shifts back to Denver for a Sunday finale (1 p.m. PST) where the Rapids were unbeaten this season.

Both teams had reason to feel pretty good about the first-leg result.

Even though they lost, the Rapids got that precious “away” goal, which in these two-leg playoff series can be a devastating tiebreaker.

On the other hand, the Sounders continued their torrid streak, especially at home. They are 9-0-2 in their past 11 matches at CenturyLink Field.

All the Sounders need to do in Colorado to earn a berth into the MLS Cup is win or tie in Denver.

The match’s decisive sequence came on a mad scramble in the Colorado penalty box early in the second half.

After the ball pinballed around among three players, it came to Lodeiro on the right side. As he pivoted toward the goal, he was taken down from behind by Colorado’s Marc Burch.

Head referee Chris Penso immediately awarded Lodeiro a penalty kick, which he converted for his fourth goal in these MLS playoffs.

As has been the case since his arrival in July, Lodeiro was the catalyst behind a relentless attack.

In the first eight minutes, he played two crosses that led to golden scoring opportunities — one to Nelson Valdez in the fifth minute, and the other to Jordan Morris in the sixth minute.

Lodeiro capped the first 10 tone-setting minutes with a 15-yard blast that goalkeeper Zac MacMath cradled in his arms.

Even with all of Seattle’s heavy pressure, it was Colorado which netted the first goal.

Midfielder Jermaine Jones’ pass got through the first line of players untouched, directly to forward Kevin Doyle on the left side of the penalty box.

Doyle had a brief opening as goalkeeper Stefan Frei came up. He tried a soft liner that, at the last minute, deflected off defender Chad Marshall’s right leg and easily landed in the back of the net in the 13th minute.

Six minutes later, the Sounders evened it at 1-1.

Cristian Roldan, the University of Washington product, sprinted up the left hash. He blasted a 20-yard shot that clunked off the left post.

The ball came right to the feet of Morris, who fired in the rebound for his 13th goal of the season — and first in the postseason.

The win Tuesday marked the 14th time the Sounders have beaten the Rapids, most all-time against any MLS opponent.