Ronaldo's first appearance since injuring his knee in the Euro 2016 final was curtailed with his 65th minute substitution despite opening the scoring in Real Madrid's 5-2 win against Osasuna on Saturday.
The Portuguese player's reluctance to rest is a sore point for Zidane, who saw his star man injured in the latter stages of last season after playing 34 consecutive league games without being substituted and 10 straight Champions League games.
Ronaldo was forced to miss crucial league games and the first leg of Real's Champions League semi-final against Manchester City with a hamstring injury.
Even after recovering he was far from his peak powers in the final games of the campaign, even though he converted the decisive spot kick in the penalty shootout to settle the Champions League final.
Ronaldo suffered more fitness woes at Euro 2016, forced off in the first half of the final with a knee injury that kept him sidelined for the start of this season.
Newspaper Marca reported last week that Zidane's plan was for Ronaldo to be eased back in gradually, indicating that he would play 70 minutes against Sporting, but the coach has now said the intention is for Ronaldo to complete the game.
"The idea is for him to play 90 minutes. I try to speak to Cristiano about other things than minutes because if you ask him he always wants to play 90 minutes," Zidane told a news conference on Tuesday.
"I'm always thinking about the two months he was out because that's a long time for a player ... (But) he's ready, we'll see what happens."
Ronaldo's footballing education had begun at Sporting, having joined the club's academy as a child, though he spent only one season in the first team before signing for Manchester United in 2003.
He last faced Sporting in the group stage of the 2007 Champions League, scoring in two victories for United, and has yet to face his old club with Real.
"Of course it's special for him because it's his club and he grew up there, but he's very professional and he will give everything as he always does," Zidane said.
"He'll be focused from the start."
(Editing by David Goodman)
