Colombia midfielder James Rodriguez has rued the absence of "vital" team-mates who are set to miss the World Cup through injury.
Radamel Falcao is the notable absence from Jose Pekerman's squad, while Aldo Leao Ramirez, Edwin Valencia and Luis Amaranto Perea have also been ruled out of the tournament.
And James, who plays his club football at Monaco with Colombia team-mate Falcao, insists the squad have not forgotten the men who helped them to qualify for the finals for the first time since France 1998.
"The group is sad because four really good players – who were vitals in the play-offs - left the camp, but we have to change our way of thinking and start to think about Greece," he told reporters.
"We are adults who already suffered these kind of situations, so we just have to play and win against Greece and the rest of the games."
Colombia are competing in Group C, with their clash against Greece in Belo Horizonte on Saturday followed by meetings with Ivory Coast and Japan.