Supporters' Shield leader Toronto FC extended its MLS winning streak with a derby victory over the Montreal Impact, while the Seattle Sounders and Portland Timbers played to a draw and the LA Galaxy were swept aside by the San Jose Earthquakes.
Sebastian Giovinco scored twice as Toronto defeated the Impact 3-1 on Sunday for its fourth consecutive win.
The former Juventus forward broke the deadlock four minutes before halftime, curling a stunning free kick past Montreal goalkeeper Evan Bush.
Jozy Altidore — named in the U.S. national team's squad for CONCACAF World Cup qualifiers against Costa Rica and Honduras — doubled the lead seven minutes into the second half.
Ignacio Piatti reduced the deficit in the 92nd minute but Giovinco restored Toronto's two-goal cushion a minute later as he took his season tally to 15 goals.
Toronto is nine points clear in the race for the Shield, while the Impact are seventh in the standings — trailing Atlanta United for the final Eastern Conference playoff spot on goal difference.
Elsewhere, the top two teams in the Western Conference met as the Seattle Sounders and Portland Timbers played to a 1-1 draw at CenturyLink Field.
U.S. call-up Cristian Roldan opened the scoring for the hosts, poking home from close range in the 18th minute.
But their Cascadia Cup rivals drew level in first-half stoppage time, with Darren Mattocks drawing a penalty before Diego Valeri converted from the spot.
The Sounders were reduced to 10 men in the game's dying moments, with Nouhou Tolo seeing a red card for an off-the-ball challenge on Portland's Diego Chara.
And it was a day to forget for 10-man Galaxy, who crashed to a 3-0 defeat at home to the Earthquakes.
Substitute Nathan Smith was sent off in the 57th minute after Valeri Qazaishvili put the Earthquakes ahead in first-half stoppage time.
And the floodgates opened as Marco Urena and Chris Wondolowski condemned the lowly Galaxy to a fourth consecutive defeat.
Winless in 10 matches, the Galaxy are second from bottom in the Western Conference. The Earthquakes are sixth, edging FC Dallas for the final playoff slot on the wins tiebreaker.