"They're one of the best teams in the world," said Simao, who will face the European champions in Cape Town on Tuesday. "They have a style of play like Barcelona, with lots of players from Barca, who play with two or three touches of the ball.
"But it's 50-50. Without showing them a lack of respect, we're not scared at all. We've got a great team too. And to become better, we have to beat Spain. They're champions of Europe, but we have our own qualities."
Spain have already been beaten at the tournament, losing 1-0 to Switzerland in their Group H opener, and Simao says the key to defeating Vicente del Bosque's men is to put them under pressure and strike on the counter-attack.
"You have to be aggressive. I don't mean committing fouls, but pressure the ball carrier and play our own game," said Simao, who plays for Spanish club side Atletico Madrid, with whom he won the UEFA Europa League last season. "They like keeping the ball, but it's not always the team that has the ball that wins. For the tactics, I don't know. It's the technical staff that decide."
Simao says Portugal will take heart from Switzerland's shock victory, but says they will not emulate their tactics to the letter. "They were a well-organised team," he said. "We'll defend well, but we're not going to play like Inter Milan against Barcelona (in the second leg of the Champions League semi-final, when Inter defended on the edge of their penalty area after being reduced to 10 men)."
Spain's 2-1 defeat of Chile in their final group game gave them top spot in the pool and ensured they avoided Brazil in the second round. Portugal were drawn in the same group as the five-time champions and secured a 0-0 draw when the sides met in their final Group G match. Having already come up against Brazil, Simao believes his side are just as capable of making life uncomfortable for Spain.
"It's normal that they (Spain) want to avoid Brazil," he said. "But we're strong as well and I think we'll give them at least as many problems. Instead of talking about Spain all the time, we need to focus on ourselves."
Portugal's chances of success depend to a certain extent on the form of their star forward and captain Cristiano Ronaldo. The Real Madrid superstar played from the left against Korea DPR but was deployed as a lone striker in the draw with Brazil. He has only scored once so far, in the 7-0 thrashing of North Korea, and Simao believes he must be given freedom on the pitch to express himself.
"My opinion is that Cristiano must be free on the pitch," he said. "But (Portugal coach) Carlos Queiroz, who knew him well at Manchester United, knows that, everyone knows that."