Although Galaxy remains third in the division after a 2-1 setback, it has only a one-point cushion over Seattle Sounders.
And while last year's MLS Cup winner has two games left to play in the regular season, Seattle has four, including a home assignment against lowly Portland Timbers on Sunday (Monday AEDT).
Robbie Keane fired Los Angeles ahead in the 18th minute against Salt Lake, connecting perfectly beyond the far post with a cross from the right and drilling a 15-yard volley across goal and into the bottom right corner.
But the team containing David Beckham and Landon Donovan was pegged back seven minutes later by Edgar Espindola who cracked a powerful low shot beyond Josh Saunders. And Saunders was beaten again in the 28th minute when Espindola flashed a header out of his reach for what proved to be the winner.
Second-placed Salt Lake now has a five-point cushion over Los Angeles who, was it to finish fourth, would have to take on the fifth-placed team in a play-off to reach the Conference semi-final stage.
New York Red Bulls are also proof that big-name players do not necessarily bring results.
New York has Tim Cahill and Thierry Henry in its ranks but it was Dutchman Sherjill MacDonald who shone for Chicago Fire.
MacDonald scored both goals in a 2-0 win for Chicago, netting in the 65th and 78th minutes as Fire jumped to second in the Eastern Conference. New York began the day second but fell to fourth, overtaken by Chicago and DC United who was a 1-0 winner at Toronto FC thanks to an 88th-minute goal from substitute Hamdi Salihi.
Montreal Impact can no longer reach the play-offs after a 1-1 draw at Houston Dynamo, for whom the result was also a setback.
Will Bruin put Houston ahead after 44 minutes, and Sanna Nyassi netted a 66th-minute leveller.
Houston stays fifth in the Eastern Conference but its two-point cushion over the Columbus Crew is a fragile one, with the Crew able to overtake it with its game in hand should it beat leader Sporting Kansas City on Sunday (Monday AEDT).
There are no such concerns for San Jose Earthquakes, who is certain to finish top of the Western Conference.
It was a 4-1 winner away to Colorado Rapids, with Chris Wondolowski's hat-trick doing much of the damage.
Marvin Chavez put San Jose ahead after two minutes, before Wondolowski took over, netting in the 11th, 51st and 83rd minutes. Andre Akpan scored a 90th-minute reply for Colorado.
Jack McInerney's 73rd-minute goal gave Philadelphia Union a 1-0 home win over New England Revolution, who had Benny Feilhaber sent off late on.