Vela equalled Josef Martinez's record for most goals in a season, taking his tally to 31 in Los Angeles FC's 1-1 draw with Minnesota United.
The Mexican star put LAFC ahead with a superb curling strike from inside the area in the 70th minute at Allianz Field.
However, Michael Boxall headed in an equaliser for Minnesota, who trail LAFC by 16 points in the Western Conference.
Meanwhile, Zlatan Ibrahimovic netted his 29th goal of the season in LA Galaxy's 4-3 loss to Vancouver Whitecaps.
Real Salt Lake secured a play-off berth courtesy of a 2-1 victory at home to Houston Dynamo.
Corey Baird needed just 35 seconds to put RSL ahead, but Tomas Martinez cancelled out the opener.
However, Jefferson Savarino's fine strike into the bottom corner from the edge of the area helped Real Salt Lake advance to the play-offs from the Western Conference.
New England moved through after a 2-0 win over New York City, which wrapped up top spot in the east.
Teal Bunbury and Gustavo Bou scored second-half goals for the Revolution.
Elsewhere, Bojan Krkic scored in Montreal Impact's 1-1 draw with defending champion Atlanta United.
Jordan Morris' late winner saw Seattle Sounders edge San Jose Earthquakes 1-0 as both teams finished with 10 men, Sporting Kansas City and Portland Timbers drew 2-2 and Colorado Rapids beat Dallas 3-0.
Chicago Fire and Toronto drew 2-2, Columbus Crew overcame Philadelphia Union 2-0, New York Red Bulls and DC United played out a 0-0 draw and Cincinnati drew 1-1 with Orlando City.