The Belgian designer - currently at Jil Sander - is said to be close to signing a deal with the French fashion house to replace John Galliano as the label's creative director, but Valentino isn't convinced.
He told vogue.co.uk: "I'm not sure - it's an amazing job, I don't know if he would be the right person for it. John Galliano is difficult to replace. I think it's important not to jump into things. It needs to be a logical continuation of the brand. But who am I to say anything? I guess we all just have to wait and see."
In September, Dior claimed they would announce the name of Galliano's successor imminently.
Bill Gaytten, acting head of design for the label, explained The Fashion house has experienced a "tough period" since the former creative director was sacked earlier this year after being accused of racism and anti-Semitism.
He said: "It's been a tough period, but what can I say?
"My lips are sealed, but all will be revealed."
A source close to LVMH, the parent company of Dior, explained: "For Dior, it's a pretty tricky situation, as the three frontrunners really can't take the job.
"Haider Ackermann is said to be 'way too edgy' for Dior; Marc Jacobs wanted the job a lot, but LVMH wants him to stick with Vuitton; and Riccardo Tisci simply refused, saying that he was feeling more than comfortable with the job at Givenchy. So nobody's taking over so far."