The Aug. 7 semifinal matchups in the 100th U.S. Open Cup are set:

D.C. United at Chicago Fire, 8:30 p.m. ET

Portland Timbers at Real Salt Lake, 9:30 p.m. ET

The winners will meet for the championship Oct. 1 or 2, venue to be determined through a random draw.

Quarterfinal results:

D.C. United 3, New England Revolution 1 (2,918 at Maryland SoccerPlex)

My match report is here.

Chicago Fire 5, Orlando City 1 (6,893 at Toyota Park)

The Fire scored four goals in the final 31 minutes and the USL side finished with nine men after red cards in the 71st and 86th minutes.

Portland Timbers 3, FC Dallas 2 (3,889 at FC Dallas Stadium)

The Timbers scored three times between the 61st and 72nd minutes to overturn a 1-0 halftime deficit.

Real Salt Lake 3, Carolina RailHawks 0 (10,287 at Rio Tinto Stadium)

Goals in the 35th, 50th and 86th minutes knocked out the NASL visitors.

The Open Cup has provided a life raft for United, which is drowning in MLS’s regular season. It has offered a boost for resurgent Chicago and provided another platform of success for Western front-runners Portland and Real Salt Lake.

United has scored eight goals in 16 league matches; it has scored six in the past two Open Cup games. Against New England, Chris Pontius and Dwayne De Rosario partnered effectively on the frontline, John Thorrington brought patience and composure to a central midfield anchored by Perry Kitchen and homegrown defender Conor Shanosky had another encouraging performance in central defense.

Would you believe United scored directly off a corner kick? DeRo’s game-winner was a looping header in the 69th minute. [Video of the goal is cued up here.]

Ben Olsen likes what he is starting to see from his captain.

“He’s been a real stud these last couple of weeks, and he looks like he has that edge again. He has a little bit of a different look in his eyes.”

Olsen suggested De Rosario’s omission from Canada’s Gold Cup roster provided extra motivation.

“No, hell no,” DeRo said. “I play for this club, this organization, to win. I don’t dwell on that stuff. … I’m focused on this cup game. It’s a huge game and I like these big games.”

DeRo said he was “disappointed” in not being selected to represent his country, but “this Gold Cup is an opportunity for a lot of people to see new faces.”

United’s other Canadians, defender Dejan Jakovic and midfielder Kyle Porter, were not called up either. Jakovic would have been selected if not for an adductor strain that has bothered him for weeks and Porter is an alternate.

Meantime, sources told the Insider that goalkeeper Bill Hamid has been selected for the U.S. squad heading to the Gold Cup. Real Salt Lake’s Nick Rimando and either Houston’s Tally Hall or Chicago’s Sean Johnson will complete the goalkeeping corps. (My guess is Johnson.) Juergen Klinsmann will announce the 23-man roster late Thursday morning.

Hamid is scheduled to report to camp in San Diego by Monday. If the Americans reach the July 28 final, he would end up missing four league matches and the July 12 friendly against Chivas Guadalajara. Joe Willis, who started Wednesday in the Open Cup, becomes Olsen’s first-choice keeper, with Andrew Dykstra in reserve.

Pontius scored for the second time in five days. This one came a few minutes after squandering a partial breakaway.

“I was thinking to myself, ‘Geez, how’d I miss that first one?’ So I had to make up for it with the second one. Actually, I tried hitting the first one with the outside of my foot and completely mis-hit it. I was glad to pull one back for the team.”

United returns to league play Saturday night at RFK Stadium against the Vancouver Whitecaps.

“Can we turn it around now against Vancouver?” Olsen said. “Again, putting so much into [the Open Cup] to get a result, we’re going to have to make some changes. But I think our spirit right now [will allow us] to start doing a little bit better in the league.”