The Borussia Dortmund midfielder claims he learned a lot from the Portuguese star during his time at Real Madrid, and revealed he still chats with former boss Jose Mourinho
Sahin ended a torrid spell at Santiago Bernabeu to return to Borussia Dortmund earlier this season, after failing to impress during a brief loan spell with Liverpool at the start of the campaign.
Despite his disappointing time with the Liga champions, the Turkey international insists he was happy to have made a "dream" move to the club, as well as the chance to learn from the likes of Ronaldo.
"It was a great opportunity to play with him [Ronaldo]," he told AS. "He is an incomparable professional, he's incredible. In one year, I learned a lot from Cristiano. Maybe some people will not think so, but he is very humble and friendly.
"Moving to Madrid was a dream. I did it. I had an injury in the first training session, and if that had not happened, I'm sure it would have been different for me.
"But that is football. I don't want to return to the past. I'm at one of the best teams in the world, I never let my head drop and I think I will be very successful."
Sahin revealed he still talks to former boss Jose Mourinho by phone, and feels Los Blancos' victory over Manchester United in the Champions League could be a turning point for the Portuguese coach and his players this season.
"We often talk by phone. We chat about football, and life in general," he went on. "The coach feels good. I think the game against Manchester United was very important for Real Madrid. He is now in a perfect position.
"They're doing a great job. It's not easy to beat Barcelona twice. The truth is that Madrid are one of the great favorites for the Champions League.
"I hope we win it, Borussia Dortmund. Madrid always want La Decima. I know they are preparing to go for it."