Both MLS teams are away in the first leg. United faces a much easier task in Kingston, Jamaica, at the Harbour View Stadium (Fox Soccer Channel, 8 p.m. ET); Houston plays CSD Municipal at the inhospitable Estadio Mateo Flores in Guatemala City (FSC, 10 p.m.).
Yet for both teams, which between them have won three of the last four MLS Cups and a combined 31 league games last year, the opposition is less important than getting their changes squared away.
During the offseason, Houston lost attackers Nate Jaqua and Joseph Ngwenya to Austrian clubs and defender Ryan Cochrane to San Jose in the expansion draft. In their places are young Argentine forward Franco Caraccio and developmental player Chris Wondolowski, and ex-United defender BobbyBoswell.
Coach Dominic Kinnear won't have defender Pat Ianni and midfielder StuartHolden during the CONCACAF quarterfinals. They are also on CONCACAF duty -- as members of the U.S. under-23 team attempting to qualify for the 2008 Olympic Games. Midfielder Brad Davis has been hobbled in preseason by a leg injury and isn't expected to play until the second leg of the quarterfinals.
But the core of Houston's '06 and '07 championship teams is still in place: keeper Pat Onstad, defenders Wade Barrett, Craig Waibel and EddieRobinson, midfielders Dwayne De Rosario, Brian Mullan and Ricardo Clark and forward Brian Ching. Richard Mulrooney, who arrived in a trade last April, adds another element of continuity Houston will need in this series, and in the semifinals if it should advance.
Caraccio scored his first goal for Houston Sunday at the TPSF in a 1-1 tie with United, which began the game with most of its likely starters: goalie ZachWells, defenders Bryan Namoff, Gonzalo Peralta and Marc Burch; midfielders Fred and Clyde Simms; and forwards Luciano Emilio and JaimeMoreno.
Cezar, who cannot play in the CONCACAF competition because he has yet to sign a contract, scored for United. His trial will continue, as will that of Dane Murphy.
If Houston's look is a shade or two different, United is the MLS version of Extreme Makeover.
Wells and Peralta are among United's newcomers. Gone are Troy Perkins, Josh Gros, Christian Gómez, Brian Carroll, Boswell and Greg Vanney, all of whom played at least 15 games last year.
United is more Latin, with Argentine midfielder Marcelo Gallardo the most renowned of foreign imports that include defenders Peralta (Argentina) and Gonzalo Martínez (Colombia), goalie José Carvallo (Peru), and forward Franco Niell (Argentina), as well as English midfielder Dan Stratford.
Former teen sensation Santino Quaranta has come back to D.C., and powerful teenager Quavas Kirk, acquired from the Galaxy in exchange for Vanney, gives coach Tom Soehn additional midfield options. Combative midfielder BenOlsen is still recovering from multiple offseason ankle surgeries and isn't available.
Soehn is running short of time to hone Peralta and Martínez as the central defensive pairing, work Gallardo and Niell into his attack, and balance the abilities of Wells and Carvallo before D.C. opens MLS play March 29 at Kansas City. Reserves and trialists garnered much of the minutes in Texas, but this two-game series against beatable opposition is likely to be the last of the experimental opportunities.