Nicolas Lodeiro was crucial for Seattle as they secured a 2-1 win at home to Real Salt Lake, while Orlando settled for a draw away to Chicago.
Seattle Sounders reasserted their play-off claims in the MLS Western Conference, securing a 2-1 win over Real Salt Lake at CenturyLink Field on Sunday.
Nicolas Lodeiro was influential as the Sounders led 2-0 at the interval, scoring and assisting for Jordan Morris.
Lodeiro's goal in the 24th minute - a fine first-time finish after a square ball into the penalty area from Andreas Ivanschitz - handed Seattle the lead and momentum.
Seattle again found space on the left flank when Lodeiro assisted Morris, who confidently headed home in the 37th minute.
Seemingly with the match in hand, Stefan Frei's loss of possession handed RSL a lifeline, with Joao Plata halving the deficit just past the hour-mark, while Clint Dempsey's late penalty rattled the crossbar for Seattle.
The Sounders sit five points adrift of reigning MLS Cup champions Portland Timbers and the sixth play-off spot, but with two games in hand.
In the Eastern Conference, Orlando City failed to leapfrog DC United, letting their lead slip to draw 2-2 at Chicago Fire.
Orlando initially went down after failing to clear their lines from a corner on six minutes, John Gossen's tame effort from distance creeping in.
The visitors equalised a mere three minutes later, when Cyle Larin got on the end of Kaka's lofted pass to poke the ball past Fire keeper Sean Johnson.
Kaka was quickest to react to hand his side the lead in the 32nd minute, in position to put away Larin's header when it rebounded off the post.
An unmarked Razvan Cocis restored parity with 12 minutes remaining after powerfully heading past Joe Bendik from David Accam's delivery.
The draw means Orlando and DC are locked on 27 points, with the latter securing six wins compared to Orlando's five, while New England Revolution sit a point behind.
In the last match on Sunday, lowly Houston Dynamo held Toronto FC to a 1-1 draw.