Bale was left out of the squad for the game following the calf strain which forced him off in their 3-1 victory over Borussia Dortmund in the Champions League last Tuesday.
"We will see tomorrow [how he is]", Zidane said when asked about Bale's availability during Saturday's pre-match press conference.
"I'm not anxious about the BBC, we will see them all soon". It's a muscle fatigue, it's nothing serious. "But here we do not like to take risks if a player has something small. He could be available".
Wales play in Georgia on October 6 and host Republic of Ireland three days later, with Chris Coleman's side now second in Group D, four points behind leaders Serbia and one ahead of third-placed Ireland.
"I'm not going to get involved in issues between the club and Cristiano Ronaldo, but I don't think that there's any problem between them", Zidane said.
"It depends on him, on his state of fitness".
It seemed nearly inevitable that the political discourse of the day would also find its way into Sunday's clash, with BBC News reporting 761 people were injured by police attempting to stop the voting in the Catalan referendum.More news: Pitbull Sends Plane To Evacuate Cancer Patients in Puerto Rico
Madrid started the weekend lying sixth in LaLiga and already seven points adrift of leaders Barcelona. However, Madrid have yet to win at the Bernabeu this season, and Espanyol have pulled off some impressive draws this season.
Zinedine Zidane's side have picked up just 11 points from a possible 18 in La Liga so far.
He said: "We're not living in the past". "It's true we dropped points in La Liga, but tomorrow we have a chance to change things". They do have a home win in the Champions League and in the Spanish Super Cup, but that lack of home success in the league is holding Madrid well down the table, in a position that's left fans and players alike agitated and unsatisfied. "If we could play every match here then that would be much better".
And, this comes with Marcelo and Theo Hernandez also out.
Espanyol had a slow start to the campaign and the team coached by former Madrid defender, Quique Sanchez Flores have traditionally been easy game in the Bernabeu.
"You will see on Sunday if he plays".