Cristiano Ronaldo is having a weaker season but still has plenty to offer Real Madrid, former Brazil international Savio has said.

Ronaldo has 32 goals and 12 assists in 40 appearances in 2016-17 and is on course to win a LaLiga and Champions League double with the capital club.

However, the Portugal international's form has been far from consistent, having failed to score in six consecutive European matches prior to the quarter-final win over Bayern Munich and netting just once in his last five league appearances.

Savio says it is no surprise to see top-level players suffer something of a blip but he insists that Ronaldo should remain a pivotal part of Zinedine Zidane's plans.

"We are accustomed to seeing Cristiano Ronaldo score 40, 50, 60 goals every year," the 43-year-old, who won three Champions Leagues with Madrid, told Omnisport. 

"It's natural and also normal in football, sometimes, to go down or to go up, to alternate your performance.

"Cristiano Ronaldo is not in the best rhythm this season, like in previous ones. But if you check Cristiano's numbers, they still are very important numbers, very strong numbers.

"Maybe it's his physical form, I don't know... but it's difficult to maintain such a regular and high performance for five, six, seven seasons. But I think he still has a lot of football to give."

Madrid host city rivals Atletico Madrid in the first leg of the semi-final on Tuesday, looking to maintain their record of just one defeat in the last seven encounters with Diego Simeone's side.

Savio believes Atletico's strength as a unit and the individual brilliance of the likes of Antoine Griezmann make them a formidable opponent over two legs.

"It's a complicated match for Madrid every time," he said. "[Atletico] are a very well worked and trained team, with a very important tactical game and nowadays players with lots of technical quality, like Griezmann and others.

"But when you are talking about a derby you can't say that one team is better than the other, or one team is playing better. In a derby, anything can happen.

"I went through many derbies in Spain, in France, in Brazil and it's something different but Madrid can go through to the next stage one more time. But it's going to be very tough because there are two matches ahead.

"When you play these matches you must be very cautious, be aware and have a good strategy. That's very important."