Dallas’ Carlos Ruiz stabbed home Mauro Diaz’s flick pass in the 89th minute to give the hosts a 2-1 victory over Seattle on Sunday, moving back to the top of the overall MLS standings with one round to play.
Dallas moved two points above Colorado, which lost at Portland, and can clinch the Supporters’ Shield for the best regular season record next weekend at Los Angeles.
In other key games, D.C. United clinched a playoff place with a 3-1 win against New York City, which dropped three points behind rival New York in the fight for top spot in the Eastern Conference, and Montreal also sealed a playoff spot with a home draw against Toronto.
Seattle went ahead at Dallas in the 41st minute via a Nicolas Lodeiro free kick, but the home team equalized in 79th through Maximiliano Urruti.
With the top six in each conference qualifying for the playoffs, Seattle is a precarious fifth in the West, only a point ahead of the two teams below them: Sporting Kansas City and Portland.
Colorado dropped below Dallas after losing 1-0 at Portland, with the sole goal coming from a Fanendo Adi penalty in the 35th minute.
The defending champion Timbers won their fifth straight at home and pulled even in points for final playoff spot in the West.
D.C. United booked its place in the playoffs with a 3-1 victory over New York City, led by Patrick Mullins, who scored one goal and set up another.
Bobby Boswell and Rob Vincent added goals to help United win its fourth straight.
City was eliminated from the Supporters’ Shield race. David Villa scored for NYC; his 22nd of the season.
Toronto’s Tosaint Ricketts scored in the 87th minute to give the visitors a share of the points in a 2-2 draw at Montreal.
Ignacio Piatti scored both goals for the Impact, who clinched a playoff spot.
Jozy Altidore also scored for Toronto, which moved within a point of second place in the East, which yields home-ground advantage and a bye in the first round of playoffs.
New York sealed one of those top two spots by defeating Columbus 3-2.
Bradley Wright-Phillips scored his 22nd and 23rd goals of the season to break a tie for the Golden Boot lead, while Mike Grella also netted for the Red Bulls.
Adam Jahn and Harrison Afful scored for Columbus.
Real Salt Lake missed a chance to seal a playoff spot as they were held to a scoreless draw by Sporting Kansas City, which remained within two points. Four teams will fight over the last three West berths next weekend.
Los Angeles clinched a home game in the playoffs by winning 1-0 at Houston, with Alan Gordon scoring in the 72nd minute.
Philadelphia also missed an opportunity to seal a playoff berth as they were beaten 2-0 at home by out-of-contention Orlando City.
Vancouver goalkeeper Paolo Tornaghi had a clean sheet in his first MLS start as the Whitecaps drew 0-0 at San Jose in a game with no playoff implications.
Chicago knocked New England out of playoff calculations by beating the Revolution 2-1.