Deep runs in the competition are rare for clubs from outside Major League Soccer. But Sacramento already knocked off three M.L.S. teams, and Orlando City looms on Wednesday.Professional soccer teams from cities like Omaha, Richmond or Detroit get only one chance a year to take their shots at opponents from America’s top league, Major League Soccer. That comes in the U.S. Open Cup, a competition for clubs at all levels that dates to 1913.M.L.S. teams have dominated the Cup since they first entered the competition after their league’s formation in 1996. Only the Rochester Rhinos, in 1998, have lifted the trophy as a lower-league team since then, and in the two decades since only one team from outside M.L.S., the Charleston Battery in 2008, had made the final.This year, Sacramento Republic, a team in the second-tier United Soccer League, has knocked off three straight M.L.S. teams in the Open Cup to advance to the final in Orlando, where it will have a chance to match Rochester by beating Orlando City on Wednesday night.“There is a gap, there’s no getting away from that,” said Coach Mark Briggs of Sacramento. “Over the course of a 35-game season, that gap would be shown pretty well. But that gap could shrink on a one-off occasion.”Coach Mark Briggs has led Sacramento to three wins over M.L.S. teams in the Cup run.Josh Pierce / Republic FCWe In the case of Sacramento, one-off wasn’t enough.After three early-round wins, Sacramento found itself in the round of 16 in May, hosting the San Jose Earthquakes, an M.L.S. team with a larger squad, more expensive players and far more resources. Republic beat San Jose, 2-0, then topped the Los Angeles Galaxy away from home as well, 2-1, in June. The Republic edged Sporting Kansas City on penalty kicks in July in the semifinals.The run has offered the team’s players, used to competing in the second-tier U.S.L., chance after chance to show how they measure up against a league that is, in most other respects, walled off to them. Those are chances they have missed for two years after the 2020 and 2021 Cups were canceled by the pandemic.“It’s a good opportunity to showcase your skills against some higher-level talent, some bigger teams,” said Conor Donovan, a Sacramento central defender. “It’s an opportunity that a lot of U.S.L. players and lower-division teams relish.”Maalique Foster, a Sacramento wing, said the divide that separates the leagues can serve as a powerful motivator. “You have to give it your all to show you deserve to be there,” he said. “I always have to be better than the guys who think they are better than me, or think that I don’t deserve to be there.”Sacramento’s home semifinal in July against Sporting Kansas City went 120 minutes without a goal before it was decided in a penalty-kick shootout.With both teams perfect, Foster stepped up for the fourth penalty for Sacramento. Rather than blasting the ball left or right, he delicately chipped the ball in the center, a shot known as a panenka, as Kansas City goalkeeper John Pulskamp helplessly dived to his right.Foster said that he had decided to try the panenka after Sporting’s William Agada had an earlier penalty saved, but then was awarded a retake that he made and celebrated.“That was the one penalty I couldn’t watch,” said Briggs, the Sacramento coach. “I had a feeling that he would try to do something clever. Fair play to him for making it. I trusted Maalique to score. I just didn’t know what he was going to do with it.”Foster celebrated with a back flip — a direct response, he said, to the flip that Agada had executed to a torrent of Sacramento boos after making his retaken penalty.With both teams perfect through four kicks, the longtime Sporting player Graham Zusi had his attempt saved by Danny Vitiello. Rodrigo López then scored to send Sacramento to the final.The victories over three M.L.S. teams have been especially sweet for Sacramento officials and fans after the city was initially offered a spot in M.L.S. in 2019, only for the deal to fall apart. Todd Dunivant, the team’s president and general manager, said the team was “still keeping the door open” for a berth in M.L.S. someday.For now, though, sandwiched between games against Louisville City and Loudon United, Republic will play Orlando City, who are currently on track for the M.L.S. playoffs.Both of Sacramento’s home games against M.L.S. teams drew capacity crowds of 11,569 to the club’s lively but tight stadium, Heart Health Park.Republic FCShould Sacramento pull off a fourth consecutive upset, there will be glory, but not much remuneration. “There’s not a big windfall at the end of the rainbow for us,” Dunivant said. “I think the biggest thing for us is that it reignites the fan base. We’ve had more interest from new partners, more interest from the community, and more people coming to our games.”Both of Sacramento’s home games against M.L.S. teams drew capacity crowds of 11,569 to the club’s lively but tight stadium, Heart Health Park. “The atmosphere at our home field was electric,” Donovan said. “It was probably the best atmosphere I’ve played in in my career.”Whatever happens on Wednesday night — the final in Orlando is a sellout, too — Sacramento Republic F.C. will be remembered as a rare lower-league team to make it that far. “We don’t think we’ve achieved anything yet,” Dunivant said. “There’s one massive game yet and its going to be the hardest one yet.” More