Ronaldo joined his national team in training on Sunday, eight days after scoring the winning penalty against Atletico Madrid for Real to lift the Champions League trophy.
His presence is a boost for Portugal, who lost 1-0 to England in a friendly last week and take on Estonia on Wednesday in Lisbon in their final warm-up game.
Santos had wanted to give Ronaldo and Real defender Pepe a chance to a catch their breath before they joined the team.
“They needed to rest,” Santos told Spanish sports magazine Marca.
“It’s better for everyone that they arrive happy and with that extra bounce after achieving their aims.”
Ronaldo scored 51 goals in 48 games in all competitions for Real this season.
“If he is so important for Real, you can only imagine how significant he is for Portugal. Certainly the same or even more.
“When you have players that score 50 to 60 goals per season, and who can always score, they are of vital importance. It’s impossible to quantify.”
Ronaldo’s fitness is a concern, with tendonitis preventing him from being at his best at the 2014 World Cup when Portugal crashed out in the group stages.
