D.C. United and the Los Angeles Galaxy will face off Friday in the semifinals of the TFC Champions Cup at the Los Angeles Coliseum after winning quarterfinal games Wednesday night in Fullerton, Calif. Ben Olsen scored on a header into an empty net in the last minute of regulation to give United a 2-1 win over Costa Rica Apertura champion Alajuela. The goal came after teenager Bobby Convey’s cross fooled the Alajuela defense, leaving Olsen all alone at the far post. Carey Talley scored on a nifty half volley to give D.C. an early lead. Alajuela equalized on a penalty kick midway through the second half. The Galaxy dominated Honduran club Real Espana, but the game ended 0-0. The MLS club prevailed, 5-3, on penalties to advance. The game marked Alexi Lalas’ debut with the Galaxy after coming out of retirement. MLS got the results it was looking for in Fullerton. The bracket was such that all the two MLS teams needed to do was win their first matches and MLS would be assured of having a team in this summer’s Club World Championship in Spain. The United-Galaxy winner will meet the winner of the other semifinal match between Pachuca of Mexico and Olimpia of Honduras in the Champions Cup final Sunday at the Coliseum. Both finalists will represent the Football Confederation in Spain.