Ramos picked up a yellow card in the 55th minute of Tuesday's first leg for a foul on Paulo Dybala.
The card means Ramos will not be taking part in the second leg at the Santiago Bernabeu on April 11.
With Ramos out, Nacho Fernandez would be a likely candidate to start alongside Raphael Varane in the heart of Madrid's defence, but the Spanish defender is out for up to a month with a thigh injury.
That means that Jesus Vallejo could deputise for Madrid. The 21-year-old has made just eight total appearances for Madrid this term due to injuries and other players ahead of him on the depth chart.
With Madrid defeating Juventus 3-0 in the first leg, however, the two-time defending champions appear likely to be able to overcome the loss of their captain in the second leg.
Yellow cards are cleared ahead of the semi-final round, making it impossible for a player to be suspended for the final unless they pick up a red card in the semi-final round.