Belgium did not explain the sudden collapse of Switzerland on Sunday after losing two goals to five goals and failing to reach the semi-finals of the Champions League.
Some players felt that Belgium, who reached the final of the World Cup finals, had secured the victory, having advanced two goals in the first 17 minutes.
Roberto Martinez, coach of the Red Devils, said: "We did not play arrogantly.
Switzerland, who lost 1-0 in Brussels, won the semi-finals thanks to direct confrontations between the two teams after 9 points equal.
"It's hard to find an explanation, we started well, and then at a time when Switzerland is not left to lose," said Martinez after losing his second official game since taking over after the 2016 European Championships.
"We gave the fighter a chance to return to the atmosphere. We had to deal harder and try to understand that something was wrong. It felt even more painful after we started."
"It was a perfect match for us and we could achieve more goals," said Thomas Munir. "I think we thought we had already been trained for the last four, it's the worst game of my career."
"After 2-0 lead, I think we do not think things can get worse, but it's a very competitive game and I hope we can learn the lesson in the future," said goalkeeper Tibu Kurtwa.
Anne Hazzard, who launched Belgium's goals, described the game as "sharp." "Maybe we started better than expected and avoided complacency."
"We must learn from the mistakes, because we have received an important lesson."