The Portuguese suffered a suspected thigh injury at the Jose Zorrilla but the Blancos boss has dismissed concerns the forward could miss the Champions League final
The Portugal international lasted just nine minutes of the game at the Jose Zorrilla, sparking fears that he had suffered a recurrence of his recent hamstring problem.
However, Ancelotti has soothed initial concerns that Ronaldo could end up missing the conclusion of the Liga season and the Champions League final against Atletico Madrid on May 24.
"We'll see in the next few days how Cristiano is, but it's not a serious problem," the Blancos boss told reporters.
"He was not comfortable, though, so I changed him.
"I don't think Pepe or [Angel] Di Maria [who also picked up knocks] have serious problems either. But we'll see."
Ancelotti was more perturbed by the way in which Madrid threw away a one-goal lead against Valladolid to leave their Liga title hopes in tatters.
Sergio Ramos had given the visitors the lead with a fine free kick but Juan Ignacio Martinez's men snatched a crucial point for their survival bid thanks to an 85th-minute equaliser from Humberto Osorio.
"We controlled the game for 70 minutes but then we lost it in the last 20," Ancelotti lamented.
"It was not a question of attitude. Iker [Casillas, Madrid's goalkeeper] had not had a save to make.
"We defended too deep and then defended a set-piece poorly and lost the game."