Germany took full advantage of the numerical advantage after Pepe was sent off in the first half, and Muller was keen to stress that his experience in previous tournaments has prepared him for this summer.
"I've been involved in the last three major tournaments so I'm used to the pressure," the Bayern Munich forward told reporters.
"But to score three goals in one game - that's pretty amazing, and the goals just got better and better. It's fantastic, but the merit also goes to the rest of the team."
Germany continue their bid to reach the knockout stages against Ghana on Saturday.