The Welshman was absent for Real's 3-2 victory at Valencia before the mid-season break due to a calf problem, while he also sat out the friendly encounter with Paris Saint-Germain in Doha on Thursday.
But Bale is in contention for a place on the bench against the Liga strugglers, although Ancelotti warned that it could take time for the world-record signing to hit full fitness.
"He is in the squad and we need to make a decision if he plays or not," the Italian said.
"He is training well but we could wait a bit longer for him to be in top condition."
Ancelotti also gave an update on full-back Fabio Coentrao, who has still not fully recovered from a thigh injury sustained while playing for Portugal in November.
"Coentrao had a very hard injury in his last game with Portugal but he came back to training 15 days ago," he added. "He needs to do a pre-season and that is what he is doing, he is training a lot.
"He has nothing to worry about but he still needs 15 more days to be completely recovered."
Real return to Liga action looking to close the gap on Barcelona and Atletico Madrid in the race for the title, and Ancelotti is keen for the side to carry their end-of-year form into 2014.
"I think we ended well in 2013," he continued. "The team did well in the last two months of the year. I would like to see the same attitude in the players.
"After the holidays I see the players training very well, with nothing important to worry about. The team is in good condition. I think tomorrow will be a great game."
