where he's the club's all-time leading scorer -- after spending last season with the MetroStars, gave United a 12th-minute lead with a glancing header. Ronnie Ekelund pulled the Earthquakes level seven minutes later from the penalty spot after teammate Brian Mullan was taken down by United 'keeper Nick Rimando in the area.
But then a pinpoint pass from Moreno was masterfully converted to a goal by Alecko Eskandarian in the 39th minute to give United the lead going into the half.
In the 61st minute, Eskandarian -- last year's No. 1 pick in the SuperDraft -- was replaced by Adu, who made his long-awaited debut after being selected first overall this year. It was a quiet first professional match for Adu -- especially after late red cards put both teams a man down, but United held on for an opening day victory.
In Columbus, some real opportunism from Frankie Hejduk gave the home side the lead after a half-hour. After MetroStars 'keeper Jonny Walker deflected an initial shot, Hejduk scored on a lunging header.
Mike Magee pulled the visitors level before the break (40) with a looping header of his own, then fellow striker John Wolyniec turned home a low cross from Mark Lisi for the eventual game-winner (52). Amado Guevara gave the MetroStars their final margin of victory two minutes from time when he hammered home a rebound from close range.
The Burn returned to the Cotton Bowl after a one-year sojourn to Dragon Stadium in Southlake, Texas, and stole a victory from Colorado thanks to a late penalty.
The home side nearly had reason to celebrate in the first half when a long-range effort from Brad Davis slipped through the grasp of Rapids 'keeper Joe Cannon, but the goal was disallowed when Eddie Johnson was adjudged to have been offside.
Moments later, John Spencer hit a low shot from outside the Dallas area that slipped past Burn 'keeper Scott Garlick -- last season's starter for Colorado -- to give the Rapids the lead (38).
But Dallas pulled even 14 minutes from time after Darryl Powell was ruled to have handled the ball in the goalmouth off a corner kick, and Bobby Rhine coolly converted from the penalty kick for the equalizer. Colorado played the final three minutes a man down after Chris Henderson was sent off for a second bookable offense.
At The Home Depot Center, the visiting Revolution twice came back from a goal down, but eventually had no answers for the new-look Los Angeles Galaxy strike force.
Carlos Ruiz, who has finished atop the MLS goal-scoring charts for each of the last two seasons, opened his 2004 account with an acrobatic chest deflection to give the home side the lead after 30 minutes.
Jay Heaps tied it for New England just after the break when he scored from a narrow angle (49), but just 10 minutes later Andreas Herzog again gave the Galaxy the lead, ripping home a low drive from outside the area.
Pat Noonan hooked home a shot from almost on the byeline to again pull New England on level terms (68), but not a minute later, another new Los Angeles player, Jovan Kirovski, hit a pile-driver from just inside the area that sailed past Revolution 'keeper Adin Brown for the Galaxy victory.
In Kansas City, defense ruled as the Wizards and Chicago Fire played to a scoreless draw. The closest either team came to scoring occured when the Wizards' Diego Gutierrez saw his second-half effort hit the outside of Chicago's post. Kansas City's Chris Klein and Chicago's C.J. Brown were ejected for violent conduct in the second half.