Sami Khedira lauded the "extraordinary" Cristiano Ronaldo, saying his Juventus team-mate was a great role model.
A five-time Ballon d'Or winner, Ronaldo is widely regarded as one of the best players of all-time.
Khedira is into his seventh season playing alongside Ronaldo, having spent five together at Real Madrid before the Portuguese star joined the midfielder in Turin in 2018.
The Germany international hailed the 35-year-old's attitude and said the forward would go down as one of the all-time greats.
"Cristiano is an extraordinary footballer and a fantastic person," Khedira said on Instagram on Thursday.
"Meanwhile, we are playing together for seven years, five of them in Madrid and two with Juventus.
"Because of his skills and his ambitions, in my opinion, he is one of the best football players the world has ever known. He wants to win every time, even if it's a training session.
"He is a role model for all the people. That's the reason why he is one of the greatest footballers. I think I can consider myself fortunate, still play and train with him."
Khedira also had praise for former head coach Jose Mourinho, who signed him at Madrid from Stuttgart in 2010.
The midfielder said: "The most impressive person as a coach and person is Jose Mourinho because in fact he trusted me.
"The biggest step in my career from Stuttgart to Real Madrid after World Cup 2010 and he taught me a lot of technical stuff but also improved me as a person, he trusted me.
"I still have an amazing relationship with him, I'm still in contact with him and I follow him as a coach and as a person and that's why I choose Jose Mourinho."