Japan's Urawa Reds suffered a shock group-stage exit at the Asian Champions League with a 2-1 loss at Hanoi FC on Wednesday.
Urawa, who won the final of the previous ACL in May, had to beat the Vietnamese club to keep alive their hopes of advancing to the knockout stage.
Urawa finished second in Group J behind South Korea's Pohang Steelers after winning just two of their six matches and losing three with a draw.
Hanoi substitute Pham Tuan Hai scored the winner from the penalty spot in the 87th minute after a foul by Urawa defender Takuya Ogiwara at My Dinh National Stadium.
The loss to Hanoi guaranteed that Urawa will not be one of the three best runners-up in the East Zone.
Only the winners of each group are certain to advance to the last 16, where they will be joined by the three best runners-up from the eastern and western halves of the competition.
"It's an unacceptable result," Urawa goalkeeper Shusaku Nishikawa said. "We made a lot of easy mistakes. I wanted to help the team by saving the penalty but couldn't do that."
Dao Van Nam opened the scoring with a 53rd-minute header for Hanoi before Dutch striker Bryan Linssen canceled it out 12 minutes later.
In early October, Urawa thrashed Hanoi 6-0 at home.