If Iran can be the first team to stop Cristiano Ronaldo from scoring at this year's World Cup, the result could be historically significant.
A final score favourable enough to move Iran into the knockout round for the first time also would carry considerable personal meaning for the Asian team's Portuguese coach, Carlos Queiroz, who was once Ronaldo's coach on their country's national team.
Queiroz, who also coached Iran at the 2014 World Cup in Brazil, called tomorrow's game against Portugal "the most interesting and important match in my seven years with Iran".
"People gave us no chance but we still have chances to qualify for the second round. We'll fight for our dreams," he said.
"We know it will be difficult, but as I said before, we came here and didn't expect easy things."