The Avengers director has addressed the challenges of a Bruce Banner solo film, reports Comic Book Movie.
Whedon was asked about the possibility of making a good Hulk film during an appearance at the Glasgow Film Festival.
"Yes," he said. "But it would be very, very hard. Hulk is a tricky son of a bitch. He's the Claudio of superheroes.
"Because the problem is it's a very popular character, but it's not a superhero. Half of it's a superhero, half of it's a werewolf. And you can't structure it like a superhero movie, you can't light it like a superhero movie.
"How do you develop that? It would be extremely difficult. The one thing you would have in your favour would be Mark Ruffalo. But right now I don't know if they have plans to do that or not, because he works so well as part of a greater whole, but by himself, it's tough. I don't envy the guys who went before."
There were mixed responses to Ang Lee's 2003 Hulk movie and the 2008 reboot The Incredible Hulk.
Ruffalo received critical acclaim for his appearance as Banner in 2012's Avengers.
Guillermo del Toro has been connected to a Hulk television series, which is currently on hold.
Watch Mark Ruffalo talk about playing Hulk below: