Brazil will face Germany in Belo Horizonte for a place in the FIFA World Cup decider, though the host nation will be without star striker Neymar.
Neymar - scorer of four goals at Brazil 2014 - was cruelly ruled out of the tournament after fracturing his vertebra in the closing stages of the side's 2-1 quarter-final triumph over South American rivals Colombia on Saturday.
Luiz Felipe Scolari will also be without captain and defender Thiago Silva, who is suspended for the last-four tie.
But despite the loss of arguably the two best players in Brazil's squad, Ronaldo said he believes the Germans - contesting their fourth consecutive semi - will have their work cut out against the five-time world champions.
"If the Germans think they will find a weak, impaired, hopeless side on the pitch, because it lost one player, and even if this player is called Neymar, they will make a great mistake underestimating the quality of the Brazilian team," said Ronaldo - winner of two World Cups in 1994 and 2002.
"Brazil has never and will never be defined by one player. We have great examples in the past, with players in the same level as Neymar.
"Like Pele, who got injured at the 1962 World Cup and was replaced. Despite that, Brazil won the World Cup. We expect that whoever takes to the pitch will do their best.
"Brazil has a good strong group of players that will show that, even with the absence of Neymar, they are still the favourites."
An entire nation was brought to a standstill when Colombia defender Juan Zuniga crashed into Neymar's back, leading with his knee in a robust challenge.
FIFA's disciplinary committee vowed to study the incident following the match but Ronaldo doubts the 28-year-old will be punished.
"I don't expect anything else to be done (about the foul that led to Neymar's injury)," he said.
"It was a cowardly act, and I don't know if it will have any consequences for the Colombian player. Actually, it doesn't matter.
"We are all sad, and frightened, because we have lost the best player in our national squad."
