Chile was hit by one of the five biggest earthquakes ever recorded in late February.
"A load of things go through your head," Millar, 28, said on Friday when asked how it felt to play in his first World Cup match on Wednesday.
"The first is your family, who know how much you've fought to be in this position, and obviously we thought a lot about the people who are still suffering because of the earthquake.
"For us it's really important to be able to bring a little happiness to the whole country but above all to the people who suffered that catastrophe.
"It hit all of us but there are people who were hit harder than others. I hope we can keep cheering them up, even if only a little."
With a magnitude of 8.8, the earthquake killed over 500 people and left thousands homeless. Many Chileans are watching the World Cup in makeshift shelters or in the homes of relatives because their own houses have been flattened.
Their national team have brought a torn and mud-stained Chilean flag with them that was rescued from the rubble of the earthquake. It has been hoisted on a flagpole next to their training pitch.
Millar was born in Arauco, close to the quake's epicentre, and started his career at local side Huachipato.
He played in the heart of Chile's midfield against Honduras in their 1-0 win and is likely to start Monday's Group H match against the Swiss in Port Elizabeth.
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