Coach Alberto Zaccheroni conceded he must share the blame for Japan's failure to make their mark at the two most important competitions of his four-year tenure after the Samurai Blue were dumped out of the World Cup in the first round on Tuesday.

Zaccheroni, who won the Asian Cup and has guided the team to some impressive results against the likes of Argentina, France, Belgium and the Netherlands since he was appointed in 2010, admitted he was unsure of his future after a 4-1 defeat to Colombia wrecked the team's slender hopes of advancing to the round of 16.

The 61-year-old Italian said he would have "doubts that would harbor inside him" after Japan paid the price for taking "the wrong approach" at this tournament and the Confederations Cup last year in Brazil, where Japan lost all three games.