The 2008 Fifa World Player of the Year is expected to lead the line for the Seleccao after a dream season at Real Madrid in which he scored a staggering 60 goals in all competitions.
Nani conceded that Ronaldo plays a crucial role in Portugal's set-up, but stressed that there is more to the national team than the 27-year-old.
"Even though many people do not accept it, Portugal do not depend on Cristiano Ronaldo," Nani told Goal.com.
"He is a great player, for me the number one, but he does not win the games on his own.
"Our opponents will be more attentive with Cristiano and that could help the rest of us, because it could allow more spaces to open up and create danger for our rivals."
Portugal have been drawn in the same group as three former European champions in Poland and Ukraine, but Nani is refusing to write off his side's chances of a top-two finish in the table.
"Our aim in this Euro is to get beyond the group stage," he explained. "With Netherlands and Germany in the group, that on its own will be a success.
"That is what really matters to us at the moment, much more than talking about a possible rival for the quarter-finals.
"Germany and Netherlands are two big favourites for the title this year. If we can knock out one of them and advance to the quarter-finals, Portugal should really be considered as a candidate [to win] in this Euro."
The 25-year-old, who moved to United in 2007, is looking to make his mark on the international stage after missing the World Cup in South Africa with an injury to his collar bone.
"That World Cup was something painful for me," he explained. "I got injured just before the training camp and had to miss out.
"And I could not get used to watching it on television because you suffer more than on the pitch.
"I do not know what would have happened had I been on the team, but we had bad luck meeting Spain in the second round."
Nani went on to talk about his situation at United, admitting that he is not satisfied with his bit-part role this season, but stressing that he still has many plans for himself at the club.
"Like any footballer, I want to play more minutes but I understand and accept what the coach chooses," he added.
"Not all of us can play, and it is a great success for any player to be at Manchester United.
"I have always said it and I do not regret it: my aim is to be the best in the world and playing at a club like United, I can achieve it.
"This season, I experienced a different and strange sensation because we did not win anything at the club.
"The last few minutes of the last game were especially frustrating with the news that came in from City.
"I do not see the Euros as a chance to prove what I can do for United. And even less so because Ferguson knows me perfectly - and that is why I am at United.
"Recognition for Portugal has nothing to do with Manchester United.
"My future? I have a contract with Manchester United and I am relaxed."