Denis Bouanga had two goals and an assist on Sunday night to help LAFC beat Austin FC 4-1 and sweep the best-of-three series in the first round of the MLS Cup playoffs.

LAFC, which won Game 1 2-1, plays at second-seeded Vancouver in the one-game Western Conference semifinals.

Son Heung-Min added a goal and an assist for No. 3 seed LAFC. Jeremy Ebobisse replaced Son in the 88th minute and capped the scoring in the third minute of stoppage time.

Son, on the counter-attack, hesitated to freeze defender Ilie Sánchez at the top of the area and then exploded toward the left end line and blasted a shot from the corner of the 6-yard box inside the back post to open the scoring in the 21st. About four minutes later, Son fed Bouanga for a finish - the 30-year-old's 100th goal across all competitions for LAFC -- into a wide-open net to make it 2-0.

Bouanga cut inside to evade defender Brendan Hines-Ike -- who fell to the ground -- and then flicked a shot into the net from the left center of the...