The Italian was named the South Americans’ permanent handler last week and will begin his new role on May 26, with a contract running until next year's World Cup finals.
His former player at the Santiago Bernabeu said that the 65-year-old has the experience needed to revive the team after their recent struggles.
"What I can say is that in football, in national teams, it's about being at the top level with a very short period of time to prepare yourself to perform," Varane told Reuters.
"So, it's a different challenge that you're facing from the day-to-day with a club.
"But I think if you're capable of winning trophies like the Champions League, and if you're capable of raising your level for big games, then you're capable of doing it anywhere, at any time.
"I think Carlo is a great coach. He has a lot of experience, so he knows how to prepare the players to perform at the right time."