Columbus Crew SC handed the Portland Timbers their first loss of the season and moved top of the Eastern Conference with a 3-2 win on Saturday.
The Timbers had started the year with three straight wins but were undone by a late goal from substitute Niko Hansen, who was making his MLS debut.
Portland took the lead in the fourth minute when Sebastian Blanco played in Dairon Asprilla, who fired across the face of goal and just inside the far post.
But Columbus equalized seven minutes later when Justin Meram tapped home a rebound following a corner kick, and took the lead in the 19th minute through Ola Kamara's audacious long-range chip.
On the stroke of half-time, Fanendo Adi was given space in the box to pull the Timbers back level. His 45th career regular season goal matched John Bain's record for most in franchise history.
But Hansen netted the winner with six minutes to play, the rookie lashing home a rebound after a diving save from Jake Gleeson.
Minnesota United's rough introduction to Major League Soccer continued on Saturday as the expansion club lost 5-2 to the New England Revolution.
Minnesota, which played in the NASL last year, has allowed 18 goals while only managing one draw through its first four games this season.
By comparison, Orlando City went 11 games before allowing 18 goals last season en route to an MLS-worst 60 goals conceded on the year. MLS teams only allowed five goals or more in seven games last season, but Minnesota has already done that in three.
Juan Agudelo gave the Revolution the lead in just the fourth minute with a header from close range, though Collen Warner was able to equalize with a well-placed shot from distance on the quarter-hour mark.
But Kei Kamara restored New England's lead five minutes later by tapping home Lee Ngyuen's cross, and Agudelo added his second goal before the break from a shot at the near post.
Brent Kallman got a goal back for Minnesota following a set piece early in the second half, but Chris Tierney answered for the Revs with a penalty four minutes later.
The New York Red Bulls settled for a goalless draw at home against Real Salt Lake.
Matt VanOekel kept a clean sheet for RSL in his first MLS start in place of Nick Rimando, who is on international duty, as are the Red Bulls' Sacha Kljestan, Derrick Etienne Jr. and Michael Murillo.
Fredrik Gulbrandsen weaved through four defenders into a clearing in the center of the box but VanOekel made the one-handed stop, diving to his right to poke it away in the 63rd minute.
Then in the 79th, he denied Bradley Wright-Phillips from close range before making another diving save in injury time, turning away Alex Muyl's shot from the top of the box.
RSL, which fired coach Jeff Cassar this week, is still searching for its first win of the season after two draws and two defeats.