Ancelotti said : “Bale will travel to Villarreal and will play. I’m not sure if he will start or come off from the bench on the right hand side of attack.”
Bale did not play for Tottenham this season before making his high-profile switch, and featured only off the bench for Wales in midweek.
Wales manager Chris Coleman said that Bale was some way short of competitive fitness.
The international break also means that Bale’s training ground time with his new team-mates has been severely limited.
Asked about these concerns, Ancelotti said: “Bale came here without having a normal pre-season but his condition is not bad. He will travel tomorrow, and he will play. He has no injuries, he is excited and very motivated.
“He’s arrived full of enthusiasm and he is very happy to be at the team he wanted to join. He is a humble player who likes to be with his team-mates. He fits in well with the squad.”
Ancelotti played down concerns over the size of the €100m fee, saying: “We have paid what the market dictated. I’m sure that there were teams that would have paid more money to Tottenham than us, but the player decided he wanted to come here.”
Bale said: “Obviously I went straight away on international duty which probably wasn’t the best but I’ve been back in the last two days now but the boys have been very nice to me and made me settle quickly and its just an honour to be here.
“I feel good, I got half an hour to 40 minutes’ game time with Wales and I’m feeling good but obviously I’m a bit behind physically than everybody else but hopefully I can catch up as soon as possible.”