"Cristiano [Ronaldo] is an extraordinary captain. You know... what kind of player he is. He has a strong positive influence on the team, both on and off the pitch. He plays a certain role, I play a certain role, but the team is the most important [component of success]. And he understands it, too," Santos told journalists.

Portugal will face 2010 World Cup winners Spain at Sochi's 43,000-seater Fisht Stadium on Friday, before playing Morocco and Iran in their other two Group B matches.

"Every member of our team is ready and understands his goals. We have a worthy rival... I can't tell you who will win. We are ready," Santos added.