He shouldered the weight of those expectations two years later when he joined D.C. United of Major League Soccer and became the youngest American athlete in more than a century to sign a major league professional contract.
With the hype behind him, Adu has reached a career crossroads as a playmaking midfielder on the United States men's Olympic team that is preparing for this week's qualifying matches.
''I'm a lot more energized,'' he said. ''I'm playing well, playing with a lot of confidence,'' adding that he was ''enjoying the game again.''
Adu's and the national team's quest to reach the Beijing Games begins Tuesday night at Raymond James Stadium in Tampa, Fla., where the United States opens Group A play against Cuba. The team then faces Panama on Thursday and Honduras on Saturday.
Canada, Haiti, Guatemala and Mexico will play this week in Group B in Carson, Calif. Two teams from each group will advance to the semifinals March 20-23 in Nashville, with the winners earning Olympic berths.
The United States team, which made its final roster cuts Sunday, can be considered a dark horse of sorts as it tries to return to the Olympics after failing to qualify in 2004. For the first time, no college players were brought to training camp; instead, the United States will work with a roster heavy on M.LS. players.
The players bonded quickly in their first international outing, playing to two gritty ties against China in December.
In the second game, goals by Robbie Rogers, Patrick Ianni and Charlie Davies forced China to rally and gave the Americans a quick tutorial on how to squander a big lead.
''It was a tough environment, but we can benefit from that,'' Coach Peter Nowak said. ''Our confidence level will come with the first win.''
Several Americans also tasted some bracket-busting success in the FIFA Under 20 World Cup in Canada last July, knocking off Brazil en route to the quarterfinals, where they lost to Austria.
Adu was the captain of that team, which included Rogers, Jozy Altidore, Nathan Sturgis, Sal Zizzo and goalkeeper Chris Seitz.
All those players, except Rogers, are members of the Olympic squad.
''That just proved we can play with the best teams in the world,'' Adu said. ''If we go out there, do what the coach asks us to and play our game, we know that we can compete.
''We've got the players, the guys in the right situations. Before, a lot of guys were college players. Now, a lot of guys are playing professionally, trying to make it in Europe or in M.L.S., and that helps us a lot.''
Four years into his professional career, Adu appears to have developed a patient and savvy approach to go with his considerable talent.
He also finds himself reunited with Nowak, his coach with D.C. United in 2004.
Nowak and Adu clashed over playing time and other issues midway through that bittersweet rookie season, which ended with Adu in a substitute role and D.C. United winning the M.L.S. championship.
''I was going through a phase where there was just a lot of pressure,'' Adu said. ''Every time you stepped out on the field you felt you had to prove yourself. Back then, I was young, man. Everybody expected me to score three goals a game. It just wasn't going to happen that way.''
Nowak said: ''He sees things right now, things he didn't see before. That's what's made me happy. We've been working on things in the past when we were together with D.C. United, and that was a difficult experience. But what we did in the past was just part of preparing for bigger things.
''Right now, he's feeling like that's what he needs to do on and off the field to make himself a better player.''
Adu, who is under contract with Benfica in Portugal, says he is playing the best soccer of his career and credits Nowak for a fresh approach.
''When I first came into the league, Peter was being cautious with me,'' Adu said. ''Now, he treats me like a full-fledged professional. He's giving me advice, not telling me what to do. It's a huge difference, and I really like it. He's allowing me to be myself, and that's been great.''