Los Blancos therefore travel to the form side being unable to count on their star duo, as they seek to regain the initiative in the La Liga title race with a win.
Ronaldo has not been training with his team-mates after experiencing muscle problems, revealed coach Zinedine Zidane in his pre-match conference on Friday.
The news arrives as a huge blow to the trainer given the Portuguese rescued Madrid against Las Palmas in midweek, scoring a brace to earn a 3-3 comeback.
The severity of the situation is compounded following Bale's two-match suspension, which was confirmed as punishment for his straight red card for wrestling Jonathan Viera to the ground.
Ronaldo's brace last time out makes him Madrid's top scorer in La Liga with 18 goals in 20 games, while Bale only recently completed his comeback from injury and will now be forced to watch his team-mates from the stands again.
Their absence would be an opportunity for the likes of Lucas Vazquez, Mariano and Marcos Asensio to impress from the start, though Madrid's task of facing Eibar on home turf without their biggest stars is a daunting one.
The Basque minnows are punching above their weight this term and targeting Europa League qualification for next season, with Jose Luis Mendilibar's men formidable in their fortress of Ipurua.
Madrid face a delicate situation, having let slip what appeared a commanding position in La Liga in recent weeks to slide into second place behind Barcelona, though Zidane's troops still boast a game in hand.
Los Blancos have won just one of their last three games - losing 2-1 at Valencia before slumping to the 3-3 home draw against Las Palmas - making a result at Eibar all the more crucial for their title hopes.