Ronaldo has not scored in Real's past two league matches, although he struck twice in their 4-3 win at Schalke on March 10.
It is the second time since La Liga's Christmas/New Year break that Ronaldo has gone goalless in consecutive league games, although the 30-year-old has still hit the back of the net five times in eight matches in all competitions.
In the lead-up to Sunday's El Clasico away to Barcelona - which is being framed as a title-decider - the Spanish media have focused on Ronaldo's scoring 'drought' but Santos is not buying the hype.
"I am absolutely certain that Cristiano will always be here [with the Portuguese national team], with tremendous ambition, a tremendous will to help out and help guide his team-mates to victory... I'm not concerned with anything," Santos said on Thursday.
The 60-year-old coach threw his support behind Ronaldo ahead of Real's trip to Camp Nou.
"I hope that he can play a great game at Barcelona," Santos said.
Real will arrive in Barcelona with 64 points, one adrift of the Catalan club, who lead La Liga ahead of El Clasico.
Portugal face Serbia in Euro 2016 qualifying on March 29 before a friendly against Cape Verde.
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