RIO DE JANEIRO — The United States men’s basketball team, undefeated in Group A, remains the prohibitive favorite to win the gold medal and its road is filled with three aging teams making a final Olympic run as a group.

With the way the Americans have played the past three games and with the familiarity Argentina, Spain and France have of Team USA, it could be the most difficult stretch to gold since the United States failed in 2004.

Team USA’s journey begins with Argentina on Wednesday evening at Carioca Arena in the quarterfinals.

If the United States wins, it faces the winner of Spain-France, teams filled with NBA experience. Team USA destroyed Argentina, 111-74, July 22 in Las Vegas, a game that might have fooled the Americans into believing the tournament would be easy.

Instead, it has been a struggle. After opening blowouts over China and Venezuela, the two worst teams in the tournament, Team USA managed a 10-point victory over a game and skilled Australian team, then was pushed to the final minute by Serbia, which could have sent the game into overtime but Bojan Bogdanovic missed an open 3-pointer in the final seconds.

Team USA was then pushed to the limit by a France team that rested six-time NBA All-Star Tony Parker. The US hung on, 100-97. Such results have left Team USA vulnerable, especially because it has been so poor defensively. Four members of the Argentina team that beat Team USA in the Athens Olympics remain on the roster.

“We will have a tough game and it might be even worse if we play the US,’’ Brooklyn Nets/Argentina forward Luis Scola had said of a potential matchup. “According to [the media], they’re struggling. But it’s just a long [tournament]. They’ve won every game they’ve played.

“Maybe they thought they were going to be playing better or beating teams by a bigger difference. Maybe people around them thought that but I wouldn’t say they’re struggling. They’ve won every game.’’

What the United States has learned is the international game is different.

Argentina could have avoided the Americans with a win Monday against Spain, but it pulled back in the fourth quarter, knowing the matchup would occur eventually, and lost, 92-73.

While Team USA features former MVP Kevin Durant, NBA Finals hero Kyrie Irving, and perennial All-Star Carmelo Anthony, the Argentinians feature 25-year-old point guard Facundo Campazzo.

He dazzled the crowd with 33 points, 11 assists, and 4 steals in Argentina’s win over Brazil Friday and leads the club in scoring.

Of course, Manu Ginobili, Andres Nocioni and Scola are still main contributors, but each is at least 36 years old and can not play the minutes or stretches as in previous years.

Wednesday’s atmosphere will be raucous, with the crowd likely 80 percent for Argentina. Their fans were so enthusiastic Monday, they chanted vigorously with their team trailing by 17 in the second half.

There has been a distinctive anti-US sentiment with some fans, who have cheered for any team playing against the Americans.

That should be the case Wednesday. This game could be the toughest for Team USA.

Gary Washburn can be reached at gwashburn@globe.com. Follow him on Twitter @GwashburnGlobe.