Johnson’s looking to score in his return to Kansas City.In the 99 years of the U.S. Open Cup, it’s never happened. But Sounders FC can make history tonight in Kansas City, Kan., where a victory over Sporting Kansas City in the Cup final would be their fourth consecutive title in this country’s oldest ongoing national soccer competition, snapping a record of three straight crowns they share with three other clubs.Unfortunately for soccer fans in general and Sounders fans in particular, tonight’s 6 p.m. (PST) match at LiveStrong Sporting Park will be broadcast only on GolTV, a low-profile, predominantly Spanish-language channel that is not included in area basic-cable packages; your best bets are to find a friend with a dish, watch the match in a bar, or listen to the radio broadcast on 97.3 KIRO-FM, featuring Kasey Keller, who was in goal for Seattle’s first three Cup triumphs.The Sounders come in on a roll, unbeaten in their past six (nine competitive matches overall, including U.S. Open Cup and CONCACAF Champions League contests) dating back to late June, and coming off their most impressive performance of the season, a 4-0 spanking of the defending MLS champion L.A. Galaxy before 60,908 here three nights ago.Sporting Kansas City, which won the Cup title eight years ago as the Kansas City Wizards, is tied with Houston for the Eastern Conference lead with 40 points from 23 matches–the Sounders, third in the West, have three fewer points from one less match–but has struggled since battling the Sounders to an ill-tempered 1-1 draw here on June 20, winning just four of 10 league contests, with four losses and two draws.In addition, Sporting KC must contend with a number of injuries to starters and one significant suspension. In June’s match, central defender Aurelien Collin was deserving of a red card for his overly physical, borderline thuggish play. In a bit of poetic justice, Collin, an MLS All-Star, will sit out due to yellow-card accumulation. In midfield, Bobby Convey started Saturday’s 1-0 win at New England but left the pitch after just seven minutes with a strained hamstring; the same injury has limited Peterson Joseph to four minutes of play over the past three matches. Up front, Jacob Peterson, who scored against Seattle in June, is doubtful with a sprained shoulder and C.J. Sapong, second on the team with five goals, is battling a strained hip. On defense, right back Chance Myers has missed the past three contests with a strained groin and center back Lawrence Olum’s effectiveness may be limited by the same injury. By contrast, the Sounders are the healthiest they’ve been all year, with every significant player on the roster available expect for forward David Estrada, who is still recovering from a broken left foot he suffered in practice in early June.The teams also took contrasting paths to the Cup final. Sporting KC received a scare in their third-round match (all 16 U.S. MLS clubs joined the 64-team competition in the third round), holding off Orlando City FC of the USL Pro League 3-2, then posted three shutouts, beating the Colorado Rapids 2-0 and the USL-Pro’s Dayton Dutch Lions 3-0, then traveling to Philadelphia to blank the Union 2-0. The Sounders hammered the North American Soccer League’s Atlanta Silverbacks 5-1 and Cal FC of the U.S. Amateur Soccer Association 5-0, then traveled to San Francisco to knock off the San Jose Earthquakes 1-0 before returning home to spank Chivas USA 4-1 in the semifinals on July 11.One thing both teams have in common is a commitment to defense: Sporting KC has surrendered a league-low 21 goals, one less than the Sounders, and has a stalwart in goal in Jimmy Nielsen, who has played every minute of every league match and recorded an 0.91 goals-against average, tops among MLS starters. Seattle has its own top keeper back in Michael Gspurning, who has started the past two matches after missing nearly three months with an injured hip. In nine starts, the 6-foot-5 Austrian has an 0.47 GAA. Seattle has played 18 U.S. Open Cup matches over the past three years, winning 17 with one draw and outscoring its opposition 43-11. This is the Sounders’ first Cup final on the road since 2009, when they won 2-1 at D.C. United. They beat the Columbus Crew 2-1 in 2010 and the Chicago Fire 2-0 last year before raucous home crowds. This year, Ozzie Alonso has scored four goals and Sammy Ochoa has added three in Cup play.Tonight’s match represents a homecoming for Sounders forward Eddie Johnson: it’s his first visit to Kansas City since 2007, when he played the last of his two seasons with the Wizards. Johnson has emerged as Seattle’s top offensive threat, with a team-leading 10 goals, tied for fifth in MLS, seven in his past nine starts. Six of the 10 have come on assists from midfielder Mauro Rosales, who leads the Sounders with nine, tied for third in the league. Fredy Montero, who rocketed in a rebound against L.A., has scored six goals and set up four others; rookie midfielders Alex Caskey and Andy Rose, both of whom broke through against the Galaxy with their first MLS goals, can’t be overlooked, either.Graham Zusi, also with nine assists, is Rosales’ Sporting KC counterpart. Kei Kamara is KC’s top offensive threat, scoring eight goals and assisting on four more.The Sounders’ previous visit to Kansas City was memorable: Rosales and Lamar Neagle scored in second-half stoppage time last August as Seattle stunned Sporting KC 2-1, handing the home team its first loss at LiveStrong Athletic Park. The Sounders are undefeated (5-0-1) in their past six against KC, with three wins in the final minutes.