Midfielder Silva, who plays for Sporting Lisbon, said Portugal would need Ronaldo to fire in Thursday's last-eight clash against Poland in Marseille if they are to make the semi-finals in France.
"It is true that Ronaldo is very important for us," Silva told reporters in France.
"It is no use beating about the bush. He scored but he also plays for the team, works for the team. He is our captain and he plays like that. He is an amazing player. We should focus on that."
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Poland, who finished second in Group C behind Germany, have scored three goals from their four matches and conceded one in the tournament.
(Reporting by Ian Rodricks in Bengaluru; editing by Amlan Chakraborty)
