The 29-year-old has scored just two goals in his 10 games at the tournament as he has struggled to find his best form, but he is adamant that his record outside of the competition can attest to his quality.
Ronaldo told reporters ahead of the game: "I don't think I have to show anyone anything.
"Look at my statistics and CV – I have no words for that question. I have nothing to prove. My career has been great so far and I just want to continue.
"For me it pushes me forward to succeed at a tournament. I like challenges, I want to do my best in whatever competition I'm in."
The Real Madrid man was an injury doubt for Portugal, but he has confirmed that he will play in his side's opener against Germany later today.