Obafemi Martins grabbed an 82nd-minute equaliser but Seattle Sounders missed the chance to book their MLS playoff place following a 1-1 draw at Houston Dynamo.
Victory would have seen Sigi Schmid's men advance into the post-season, but Dynamo - who are now officially out of the running - spoiled the celebrations after Ricardo Clark's second-half opener.
Seattle started brightly, with former Newcastle United man Martins drilling just wide of Tyler Deric's goal on the 17-minute mark in the only clear-cut chance of a cagey half.
The visitors almost took a big step into the playoffs after the break when Deric's smart save kept out ex-Tottenham Hotspur forward Clint Dempsey on 48 minutes.
Against the run of play, Owen Coyle's troops preserved their own slim chances of reaching the post-season when Clark drilled home from outside the box.
However, Seattle hit back with eight minutes of normal time left through Martins's header from point-blank range, but a point would not be enough to seal their progression on the night.
They were almost denied even that when Will Bruin connected with Alex's cross late on, but the Dynamo striker could only head wide as both sides shared the spoils.
A home win over Real Salt Lake in next weekend's final round of regular fixtures would see the Sounders advance.
