Volker Finke said Cameroon only had themselves to blame after their World Cup campaign ended with a 4-1 defeat to hosts Brazil on Monday.
The fate of the African nation had already been sealed before the Group A fixture in Brasilia, following defeats to Mexico and Croatia - the latter blighted by Cameroon's ill-discipline.
The African side showed glimpses of the talent that got them to the World Cup in the first place against Brazil and even threatened an upset when Joel Matip cancelled out Neymar's opener.
However, Neymar restored Brazil's lead before half-time, while second-half goals from Fred and Fernandinho set up a last-16 clash with Chile for the tournament hosts.
"There were times we played well but we need to work on our concentration," Cameroon boss Finke told reporters after the match.
"We lost the ball three times and conceded three goals from it. We don't seem to be able to concentrate for 90 minutes and we'll have to work on that.
"Brazil deserved to win tonight, they created more chances."