The Welshman could be rested for Saturday's match as he continues to recover from flu, but Cristiano Ronaldo will definitely feature in order to increase his fitness levels.
The former Tottenham Hotspur star was benched for the first leg of Madrid's Champions League semifinal tie against Bayern Munich in midweek and Ancelotti admits he could opt to rest the Welshman before the visit to the Allianz Arena next week, where los Blancos will defend a 1-0 lead.
"Bale is still feeling a little weak after his illness," the Italian stated at a press conference on Friday. "We will make a final decision on Saturday about whether he will play against Osasuna or if we will prepare him for Tuesday's return instead."
There was better news regarding Cristiano Ronaldo, however, with Ancelotti revealing the Portugal star has shaken off his injury problems and will feature on Saturday in a bid to bolster his match fitness.
"Cristiano did well against Bayern. He needs to play games in order to get back to his best again and he will play on Saturday," he said.
The Madrid coach admits his side was left drained by the win over Bayern but has stressed he will not make too many changes to the team against Osasuna as the club looks to keep its slim title hopes alive.
"We want to recover energy to make sure we win all games. The match against Bayern cost us a lot of energy, but we hope to be ready for Osasuna.
"We will make a few changes, but not too many because it is a crucial game for us."