St Etienne coach Christophe Galtier admitted he was struggling to come up with an explanation for his side's shock Coupe de France elimination at the hands of fourth-tier Cannes.
The high-flying Ligue 1 outfit took the lead in the 20th minute through Brandao but Cannes, who play in the Championnat de France Amateur Group C, equalised with 20 minutes to go courtesy of Mickael Darnet.
Pierre-Yves Polomat was then sent off for Galtier's men 10 minutes from the end but there were no further goals in the 90 minutes and extra time could not separate the sides.
The 1932 winners then prevailed 4-3 in the penalty shoot-out to claim a remarkable victory and move into the last 32.
"It's a disappointment. I cannot find the words," said Galtier.
"We ran, jumped and tackled to the bare minimum. But this minimum was not enough tonight in Cannes."
Galtier said his players had failed to come up the standards expected of a top-flight side.
"It was well below the level of Ligue 1. It is logical that we were knocked out," he said.
"We were too far below the professional level technically. A defeat is always collective, but some of my players are guiltier than others. I will not go into detail.
"There is no excuse. We knew what this game would be.
"It's hard, very hard. We will quickly see if the group has the quality I thought. Against Lille on Friday, we'll see if we can make a return to form.
"We are all responsible for this failure even though Cannes earned their qualification."
Cannes coach Jean-Marc Pilorget, meanwhile, was understandably delighted to see his side produce a stunning upset that secures a meeting with Championnat National outfit Plabennec in the last 32.
"It is a source of great pride for the club, for leaders who fought for years for our survival, and for my players who played the game," he said.
"There is also joy because we are conscious of having achieved something.
"Nobody was counting on Cannes qualifying ahead of ASSE, one of the four or five best teams in France."