The Azzurri goalkeeper believed that his side simply did not do enough and can have no complaints about their exit at the hands of Uruguay following a 1-0 defeat in Natal
Diego Godin's 81st-minute header was enough for la Celeste to seal the victory required to take them through to the next round in a tempestuous encounter that saw Claudio Marchisio sent off and Luis Suarez accused of biting Giorgio Chiellini.
However Buffon, reflecting on Italy's failure to reach the knockout stages for the second World Cup in succession, was critical of the manner in which his side departed the tournament.
"It's a very sad day for us as a group, as individual players and as a nation," the 36-year-old told Sky Italia.
"It was a failure and it is useless to deny it or go around it. We went out and deservedly so."
Italy were hoping to make amends for going without a win in the 2010 World Cup, where they finished behind Paraguay, Slovakia and New Zealand in Group F, and Buffon was disheartened by their inability to build on creditable Euro 2012 and Confederations Cup campaigns.
"After 2010 there were two competitions in which we performed well," he continued.
"We had a good start and let expectations maybe get too high, and at the end we struggled against the harsh reality of playing two games in which we created little and failed to score."