Colombia midfielder James Rodriguez said their playing group remains downcast due to their injured compatriots.
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 FIFA World Cup in Brazil due to injury.
Rodriguez, a club team-mate of Falcao's at Monaco, said the squad had not forgotten the men who had 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," Rodriguez said.
"We are adults who already suffered than kind of situations, so we just have to play and win against Greece and the rest of the games."
Rodriguez, 22, plied his trade at Porto prior to his switch to the Ligue 1 powerhouses, and said his experience playing in some of Europe's top leagues has enhanced his game.
"Playing in different teams has been really good," he said.
"You get more experience and that is going to help the team to play good, and I will give my best for the team."
Colombia are competing in Group C, with their clash against Greece in Belo Horizonte on Saturday followed by meetings with Ivory Coast and Japan.