The Wales international, who has not played since injuring his calf against Granada in January, was expected to return to action at the Bernabeu for Wednesday's Copa del Rey semi-final first-leg encounter with Atletico Madrid, but was instead a glaring omission from the team sheet.
Goals from Jese and Angel Di Maria followed Emiliano Insua's early own-goal to give Real a 3-0 victory in Bale's absence, which Ancelotti insisted was a tactical move given Ronaldo starts a three-match ban when Villarreal visit the capital on Saturday.
The Italian told a press conference: "There is no relapse, (Bale) is fine and I just preferred to rest him for Saturday seeing as Cristiano cannot play. Gareth being fresh will be good. He'll probably play."
Ronaldo will sit out three league games as punishment for being sent off and making an offensive gesture during Sunday's draw with Athletic Bilbao.
Turning his attention back to the result, which put Real in the driving seat to reach the cup final at their city rivals' expense, Ancelotti added: "The result is very good, but we have to be careful.
"We have to do the same thing in the return leg but it will not be easy because Atleti will try hard to recover. We have to prepare well."
Real were handed an early boost when Pepe's powerful shot deflected off Insua and went in.
They turned the screw after the break and hit Atletico twice more, first through Jese and then thanks to another deflected effort, with Di Maria pinging the ball off Joao Miranda and into the net.
"I am completely satisfied with the match, everyone has done fantastic," Ancelotti added.
"We have done well, recovered well, been very aggressive and compact.
"The dream is for the team to play like they did tonight at all times. They won a game by playing well.
"Our team showed it can play well and we must do so continuously because now every game is important."
Diego Simeone's men still lead the La Liga table but look set to surrender the cup they won at Real's expense last season.
The Argentinian was philosophical in defeat while reminding the opposition that they can expect a strong reaction at the Vicente Calderon next week.
He said: "Madrid scored twice by deflecting (the ball) off our players but beyond that there were not many scoring chances in the match.
"There will be opportunities in another 90 minutes. It's football, you still have to play the game.
"They played a very good game and we have to congratulate the opponent on the way they played.
"We tried but we could not find a way."