Ronaldo scored Madrid's stunning second goal in Sunday's 3-1 win at Camp Nou, with the return leg coming up at the Santiago Bernabeu on Wednesday.
But Zinedine Zidane's side will be without their talisman after he was booked for removing his shirt in his goal celebration, before earning a second caution for simulation.
The four-time Ballon d'Or winner's hefty punishment comes as a result of him pushing Ricardo de Burgos Bengoetxea after the referee brandished his red card.
The Royal Spanish Football Federation (RFEF) had the option of imposing a maximum suspension of 12 games for the offence, but Spain right-back Carvajal is hopeful Madrid can reduce Ronaldo's punishment on appeal.
"I think it's a bit excessive, this suspension for Cristiano," Carvajal told a pre-match news conference.
"I don't what to talk badly about the referee. For [Ronaldo] it's a very frustrating situation that they sent him off in the way they did.
"It's very excessive and I hope the committee is able to take some games off. We're all pretty down about the ban."
Carvajal also suggested there was inconsistency in the referee's decision making after Luis Suarez took a tumble over goalkeeper Keylor Navas to win a penalty that Lionel Messi converted before Ronaldo made way.
"Whether [Suarez] pretended to win a penalty or not, you can see it yourselves in the images. It's pretty clear," he said.
"Bans and decisions like this decide titles so they have to be as correct as possible."
Carvajal added: "We can't get into the heads of the referees. We have to just believe they are trying to do then best they possibly can, as players do as well
"We all commit errors. That's what happens in football."