Zinedine Zidane is open to the idea of Cristiano Ronaldo returning to Real Madrid.

Speculation has been rife following Juventus' Champions League elimination by Porto, suggesting Ronaldo wants to head back to the Santiago Bernabeu.

Despite reports only surfacing in the past week, Spanish publication AS claims Ronaldo and Madrid have been in talks for several months and a transfer for the end of the season is being mooted, with Erling Haaland and Kylian Mbappe seemingly out of reach this year.

Ronaldo left Madrid for Juve in 2018, a move seen as a major statement in the Bianconeri's bid to end their Champions League drought, which stretches back to 1995-96.

But they have not been beyond the quarter-finals since, losing to Ajax, Lyon and most recently Porto in successive years.

Ronaldo is already Madrid's record scorer with 450 goals and won Europe's elite competition four times with Los Blancos, and Zidane acknowledges another link-up is not impossible.

Asked by Sky Sport Italia if there was truth in the rumors linking Ronaldo to Madrid, Zidane said: "Maybe. We know Cristiano, the person he is and what he did here.

"But he is a Juventus player. I did what I had to do with him, now we will see what happens in the future. I was lucky enough to train him because he is really impressive."

Zidane was speaking ahead of Madrid's Champions League last-16 second leg against Atalanta, having beaten Juve's Serie A rivals 1-0 in Bergamo in their previous meeting.

Remo Freuler was sent off after just 17 minutes for the home side, with Zidane's men then finally breaking the deadlock through Ferland Mendy four minutes from time.

Madrid are in the driving seat in the tie but Zidane insists he is not relaxed heading into Tuesday's game. While he realizes Atalanta have to come out and go for goals, he is also well aware that is their main strength.

"I'm not calm, in football that doesn't exist," Zidane added. "You must have a great performance to get through the round, you can't go to 95 per cent because they will come here to win.

"We will need the best Real Madrid. I don't expect anything different from Atalanta. They always play in the same way: they attack and score, a lot. It's a great team.

"It's true that everything changed early on in the first leg, but many things were said to each other and they are rightly angry about the sending off, which was harsh. But we also prefer to play against 11 men, because then our game was also different."