"We weren't sharp enough," goalkeeper Nick Rimando said. "We weren't patient enough. It was almost like we panicked when they scored the first goal. … It just wasn't a mature effort in the second half."
Olmes Garcia scored on a bicycle kick in second-half stoppage time for RSL.
The defeat not only ended RSL's streak the club was 4-0-2 since losing to Los Angeles 1-0 on July 12 it also lifted Dallas (12-7-6) into a three-way tie for first in MLS's Western Division with RSL (11-5-9) and Seattle, which plays Sunday at Portland. All three have 42 points.
The win extended Dallas' unbeaten streak to 10 games.
RSL took an unexpected advantage into the second half when Dallas striker Blas Perez was given his second yellow card – which gave him a red card and an ejection – during a bizarre sequence of events in the final seconds of the first half. Perez was called for embellishing the effects of a shove that earned RSL's Chris Schuler a yellow as well.
"He got up and pushed Perez and Perez kind of made a meal of it and that's what he got called for," Rimando said. "I think if he just goes down normally, it's nothing on Perez, but he made it look as fancy as he could."
Schuler claimed he didn't remember anything after the initial foul.
Despite playing a man down, FC Dallas struck quickly after halftime, scoring in the 50th minute courtesy of a fortunate bounce.
As Schuler and FCD's Matt Hedges battled in front of the net for a corner kick, the ball bounded away from them, then caromed off the chest of onrushing Dallas defender Je-Vaughn Watson and into the net as Rimando stood frozen in disbelief.
"Giving up a goal from a dead ball situation can really change the tide of the game," RSL coach Jeff Cassar said. "We had a mental lapse on a set play, and from there we're chasing the game. … It just wasn't good enough the whole night."
Dallas doubled the lead in the 74th, when Fabian Castillo, who frustrated the RSL defense all night with his speed, collected a soft header from Tesho Akindele and got loose on the right wing. Castillo easily outraced Ned Grabavoy and Nat Borchers to give himself space and slid a low shot just inside the far post.
The goal gave Castillo perhaps the hottest player in MLS a streak of 11 consecutive games in all competitions with either a goal or an assist. He has 10 goals in that span.
"Castillo's got unique speed and that makes him difficult to defend," Schuler said. "You're pretty much defending the whole back space. Any long ball in bounds is his territory."
RSL travels to San Jose for a game next Saturday before a rematch with FC Dallas at Rio Tinto Stadium on Sept. 6, and Schuler said he's looking forward to that game after Friday's seemingly inexplicable defeat.
"You're up a man, you want to be putting pressure on them, then they score and have a lot of momentum," he said. "We started playing a little desperate, which is unfortunate because we're a good team and we play our style pretty successfully, but we lost that in the second half. But it won't be difficult for us to recover from this. We have a good team and good leadership, and everything will fall into place."
FC Dallas 2, RSL 1
O Real Salt Lake's six-game unbeaten streak ends, while FC Dallas is now unbeaten in 10 straight matches.
• Real Salt Lake plays the second half with a man advantage after Dallas forward Blas Perez is given a red card.
W L T Pts GF GA
Sporting K.C. 12 6 6 42 36 23
D.C. 12 7 4 40 36 26
Toronto FC 9 8 5 32 33 34
Columbus 7 8 9 30 32 32
New York 6 7 10 28 35 34
New England 8 12 3 27 30 36
Philadelphia 6 9 9 27 36 39
Houston 7 12 4 25 25 42
Chicago 4 6 13 25 29 35
Montreal 4 14 5 17 23 41
W L T Pts GF GA
Seattle 13 7 3 42 39 31
FC Dallas 12 7 6 42 45 33
Real Salt Lake 11 5 9 42 39 30
Los Angeles 10 5 7 37 39 26
Vancouver 7 4 12 33 33 29
Portland 7 7 10 31 39 39
Colorado 8 11 6 30 37 39
San Jose 6 9 7 25 26 28
Chivas USA 6 11 6 24 21 36
Los Angeles 4, Colorado 3
Seattle FC 1, San Jose 1, tie
FC Dallas 2, Real Salt Lake 1
Montreal at New York, 5 p.m.
Chicago at Toronto FC, 5 p.m.
Houston at Columbus, 5:30 p.m.
Chivas USA at New England, 5:30 p.m.
D.C. United at Sporting K.C., 6:30 p.m.
Vancouver at Los Angeles, 8:30 p.m.
Seattle FC at Portland, 3 p.m.
San Jose at Philadelphia, 6 p.m.
Dallas 2, RSL 1
Real Salt Lake 0 1 1
FC Dallas 0 2 2
Second half » 1, FC Dallas, Watson 4 (Michel), 50th minute. 2, FC Dallas, Castillo 9 (Akindele, Michel), 74th. 3, Real Salt Lake, Garcia 3 (Velasquez), 90th+.
Goalies » Real Salt Lake, Nick Rimando; FC Dallas, Raul Fernandez.
Yellow CardsPerez, FC Dallas, 31st; Michel, FC Dallas, 33rd; Schuler, Real Salt Lake, 45th.
Red CardsPerez, FC Dallas, 45th.
RefereeIsmail Elfath. Assistant RefereesEric Boria. James Conlee. 4th OfficialArmando Villarreal. Attendance » 17,622 (21,193)
Real Salt LakeNick Rimando, Chris Schuler, Tony Beltran, Nat Borchers, Chris Wingert (Olmes Garcia, 57th), Luke Mulholland (Sebastian Velasquez, 71st), Luis Gil, Kyle Beckerman, Ned Grabavoy, Joao Plata, Robbie Findley (Devon Sandoval, 80th).
FC DallasRaul Fernandez, Jair Benitez (Kellyn Acosta, 65th), Matt Hedges, Michel, Zach Loyd, Victor Ulloa, Je-Vaughn Watson, Blas Perez, Andres Escobar (Ryan Hollingshead, 70th), Fabian Castillo (Peter Luccin, 80th), Tesho Akindele.