Last year's MLS Cup finalists, Los Angeles FC and the Philadelphia Union, launched their bids for a return to the title game with victories in the opening games of the playoffs on Saturday.
Denis Bouanga and Ryan Hollingshead scored two goals each as defending champions LAFC beat the Vancouver Whitecaps 5-2 in game one of their three game, first round series.
Philadelphia enjoyed a comfortable 3-1 win at home over the New England Revolution, scoring all their goals in the opening half.
MLS has introduced a three-game series format in the opening round of the playoffs this season with penalty shootouts to determine a winner if the games end level.
While aggregate scores and goal difference therefore count for nothing, LAFC certainly sent a clear message with their demolition of Vancouver.
Hollingshead put LAFC ahead in the 18th minute when his header from a corner was saved by Yohei Takaoka but the American reacted swiftly to drill home the loose ball.
A cool finish from Brian White brought the Whitecaps level only for French-born Gabon international Bouanga, the top scorer in the regular season, to restore LAFC's lead, cutting in from the left and firing into the corner.
Vancouver responded again though with Sam Adekugbe's glancing header from a Ryan Gauld free kick ensuring the teams went in 2-2 at the interval.
But it was all LAFC after the break -- Hollingshead slotted home from close range in the 52nd minute and then Bouanga made it 4-2 with a low drive through a crowded penalty area.
Colombian defender Jesus Morillo rounded off a strong performance with a thundering header off the underside of the bar from a Mateusz Bogusz corner.
In Philadelphia, Hungarian attacking midfielder Daniel Gazdag put the Union on their way, converting a 19th-minute penalty after New England goalkeeper Jacob Jackson brought down Julian Carranza.
Danish forward Mikael Uhre doubled the advantage in the 26th minute after Kai Wagner whipped in a cross from the left that deflected off Revolution defender Dave Romney -- although Jackson was able to parry, Uhre was on hand to tap in the loose ball.
Nathan Harriel made it 3-0 with a superb header at the back post after he rose, unattended, to meet a deep free kick from Wagner.
Argentine Gustavo Bou gave the visitors some hope of a comeback with a well-taken solo goal in the 68th minute, jinking into the box before firing home a left-foot shot.
Union head coach Jim Curtin said the victory showed his team should be considered contenders again.
"It's a good reminder we're still a good team. We can beat anybody. Don't forget about us," he said.
"Overall, we're a tough out. When this group plays in elimination games, whether it's Champions League, whether it's Leagues Cup, whether it's playoffs –- we don't fold and just lose. We're a team that's tough to play against. So this format, it suits us."
New England will host game two in the Eastern Conference series on November 8.
Sunday sees Houston at home to Real Salt Lake and Sporting Kansas City at St Louis City in the West, while Eastern Conference regular season winners Cincinnati kick off their post-season bid against the New York Red Bulls.
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