Nathan Ordaz was the unlikely hero as Los Angeles FC beat Austin FC 2-1 on Wednesday in game one of their MLS Cup round one playoff series.

The 21-year-old El Salvador international was in the right place to finish off a move by LAFC's high-scoring duo of Son Heung-min and Denis Bouanga in the 79th minute.

South Korean star Son brought the ball into the box and found Bouanga, whose shot from the left side of the area took a slight deflection and was tapped in by second-half sub Ordaz to make it 2-1.

"Thank God I was onside," Ordaz said. "That actually might have been going in, but I just didn't want to risk it. So honestly, thank God."

LAFC took the lead in the 20th minute with an own-goal by Austin's Brendan Hines-Ike when Ryan Hollingshead's cross deflected off him.

Jon Gallagher pulled a goal back for Austin in the 63rd minute but the best-of-three series will head to Austin for game two on Sunday with LAFC in control.

The winner of the series will face either Dallas or Vancouver Whitecaps in the single elimination Western Conference semi-final.

The Whitecaps have a 1-0 lead in their series.