Vietnam's national team suffered a 0-2 defeat to Australia's U23 squad at the Thang Long-Hanoi 1000th Anniversary Football Cup at My Dinh Stadium on Wednesday.
The hosts' performance was in stark contrast to Monday, when they beat Kuwait's U23 squad 3-0.
The Vietnamese players, especially the midfielders and defenders, moved slowly and were often left behind by their beefy Australian rivals.
In just 30 minutes, the home team conceded two goals before they tightened their defense, but their attackers failed to capitalize on the few chances.
Speaking to the press after the match, coach Calisto said that Vietnam could have scored some goals and a 2-all tie would have been a fairer reflection of the game.
The Portuguese tactician said that his players were still tired after the opening day victory, but also conceded that the socceroos were physically stronger.
Calisto saw positives in the loss. "We made a lot of mistakes during the game. The players have seen their mistakes and will try to do better.
"We should remember that Singapore players are also big like Australians, so the game is a good chance for Vietnam."
In other action, the Democratic Republic of Korea, who defeated the Aussies 1-0 on Monday, beat Kuwait's U23 team by the same margin.
The football tournament, organized to celebrate the 1000th anniversary of Thanh Long-Hanoi, ends in Hanoi on Friday September 2. A similar contest will in Ho Chi Minh City will be played from September 28-October 2, pitting Vietnam's U23 squad against Singapore, Malaysia and Iran's U21 teams.