Thibaut Courtois delivered a damning review of Belgium's performance following Monday's 2-0 opening-game loss to Italy at Euro 2016.
Marc Wilmots' side were regarded as one of the pre-tournament favourites in France, but sit bottom of Group E after goals from Emanuele Giaccherini and Graziano Pelle handed Italy the points in Lyon.
"We were outclassed on all fronts," said Chelsea goalkeeper Courtois in quotes reported by Sportwereld. "Tactically, technically and organisationally we came up short.
"We made the same mistakes as in the friendly games. For the first we did not follow our man.
"This is a big disappointment, because the first match is very important. We could have done a great thing after the draw in the other match.
"The next two games we should be winning. We have to play better."
Next up for Belgium - the highest-ranked team at the tournament - is Saturday's match against the Republic of Ireland, who drew 1-1 with Sweden on Monday.