Cristiano Ronaldo's decision to leave Real Madrid for Juventus "should be appreciated", Andre Villas-Boas said as the Marseille coach backed the star to win the Ballon d'Or.
Barcelona star Lionel Messi is tipped to win the award for a record sixth time in Paris on Monday, while Liverpool star Virgil van Dijk is also among the contenders to take home the prize.
Messi's candidacy comes on the heels of a La Liga-winning campaign, although the Argentine's Barcelona were beaten in the Champions League semi-finals by Van Dijk's Liverpool.
The Reds went on to win the Champions League in Madrid against Spurs, solidifying the Dutchman's candidacy despite a Nations League final defeat with the Netherlands at the hands of Ronaldo's Portugal.
All three are considered possibilities to win the award, although Messi was recognized by FIFA as The Best Men's Player earlier this year for his exploits with Barcelona and Argentina.
Ronaldo is also a five-time winner of the Ballon d'Or prize, but has not been as prolific since joining Juve from Madrid in 2018.
However, Villas-Boas backed his fellow Portuguese, although he labelled both Ronaldo and Messi as extraterrestrials.
"It's difficult... I am Portuguese so of course I support Ronaldo more," he said.
"Cristiano took a risk by leaving the best team in the world, with more titles in the world. That kind of risk should be appreciated. Playing in Italy and scoring goals is difficult.
"Messi is still in his club, Barcelona, which is a big club. He is able to make the difference.
"But I am more for Cristiano because I'm Portuguese. Both of them are exceptional, it's difficult to choose. It [Ballon d'Or] will become a competition between them.
"Having these two players in the same generation and watching them is absolutely incredible. They are extraterrestrials."
Ronaldo and Juventus currently sit atop Serie A ahead of a visit to Sassuolo on Sunday.
The forward has scored six goals in 15 matches this season, having fired five of those goals in Serie A play as Juventus maintain a one-point lead over Inter atop the table.
Messi's Barcelona and van Dijk's Liverpool are also sitting atop their leagues ahead of matches against Atletico Madrid and Brighton, respectively.