Xavi -- when asked in a news conference whether it was harder to win LaLiga or the Champions League -- had said the Champions League was "more difficult" but "unfair."
"I think Leo (Messi) said the best team doesn't always win it and I totally agree. A penalty, a sending off and you're out. The league, over 38 games, is fairer," Xavi said.
"When you've won five out of the last nine Champions Leagues, it isn't about luck," Carvajal responded when those comments were put to him in a news conference on Tuesday ahead of Madrid's game with Shakhtar Donetsk.
"In the end, football is about results. Who scores more goals, and concedes fewer, wins.
"Last year we had a great season in the league and we had a Champions League with ups and downs, but we took our chances in the key moments and we won the cup. It's funny because this debate about 'fair or unfair' only comes up when Real Madrid win the Champions League. When other teams do, it's a meritocracy."
Madrid and Barcelona are currently level on 19 points at the top of the LaLiga table -- after Madrid dropped points for the first time in a 1-1 home draw with Osasuna on Sunday -- with their El Clasico meeting under two weeks away.
Madrid are top of their Champions League group F with six points from two games played as they look to retain their trophy.
"The little details are very important. It isn't about luck or bad luck," manager Carlo Ancelotti said, when asked about success in Europe.
"Talking about luck can hide the problems you have, or the merit of the opponent.
"In the Champions League you can concede three goals in six minutes -- as happened to me in [the 2005 final] -- or you can score two goals in a minute in a semi-final. They're little details but you can control them with the right attitude. I think Real Madrid are the team that has best looked after those details."
"What is the best? Everyone has their opinion," he said.
"Playing well is about a lot of things. It isn't just about having the ball, it's about defending well. You can't be successful if you only do one thing well. So it's easier to say that the best team wins the Champions League."