Paul Rudd, Craig Roberts and Selena Gomez star in the new Netflix film “The Fundamentals of Caring,” written and directed by Rob Burnett. Adapted from the Jonathan Evison novel “The Revised Fundamentals of Caregiving,” the film tells the story about a young boy with Duchenne muscular dystrophy, played by Roberts, and his caregiver, Paul Rudd, who are both equally wounded and have low prospects of getting any better. Variety spoke with director, producer and writer Burnett about why Netflix was the best venue for the project and why Rudd was the perfect fit.

What attracted you to the project?

When I read this book by Jonathan Evison, I thought he did such a nice job telling a very tragic story in a funny way. That bittersweet quality of these characters is something that always attracts me to the material.

Was it difficult to adapt the novel?

It’s difficult because the book is so good so you don’t want to muck it up. Ultimately, you want to get to a place where you realize that a movie and a book are two different things. I mostly took the plot and the relationship between Ben and Trevor and tried to capture the spirit of it and make it my own. To his credit, Jonathan loved the screenplay and the movie, which is a real testament to his generosity as an artist.

What is the one thing that you would have wanted to include in the movie but couldn’t?

I think the biggest difference between the two is that the book is told from Ben’s first-person perspective and I decided the movie to be a true two-hander with Ben and Trevor. What was interesting what that here the caregiver was just as injured as the person he’s caring for. Neither will get over their circumstances, so how do you make something heroic when they don’t really want to help each other? The growth is microscopic, but I love the little celebration in life. They go from not living to living just a little, and that will resonate with a lot of people. At the end of the day, is there anything more than kissing a girl?

How did Netflix come into the mix?

It was sort of a two-step process for us. We had a research screening for the movie in Los Angeles and the movie, quite frankly, tested off the charts. We finished the movie and then had another similar screening but invited buyers to come and see it because it played so well the first time. Again, the movie played incredibly well and Netflix Acquisitions made us a big offer for the streaming rights for the movie right before Sundance. After Sundance and our success there, we were about to map a theatrical release when Netflix came back with the other part of the company and said we want to make this a Netflix original and we were thrilled. From that moment on it’s been wholly a Netflix project.

Why was Netflix the best option instead of going through the theatrical route?

I think right now, to be a Netflix original I think carries great prestige. They don’t give that to just anyone so I’m proud of that association and the quality that that suggests. From a practical standpoint, the idea that this little movie will open Friday in 190 countries in 12 languages to 81 million subscribers, it’s kind of mind-blowing. I don’t think there’s any way a movie of this size could reach that kind of audience in any other way. Because we sold the streaming rights to Netflix first, which was unusual at the time and it was a big story at Sundance because it normally goes in a different order, once the streaming rights are gone it mutes the theatrical possibilities because you’re really pushing into theaters in order to raise the value for the streaming rights later. Since we already sold those, I never imagined that the movie would be able to get into thousands of screens, if that makes sense.

How did Paul Rudd get attached to the film?

As I was writing the script I couldn’t help but think of Paul. I reached out to him directly. We had maybe met a couple of times, but didn’t really know each other well. We know a lot of the same people just as New York comedy fellas. He agreed to meet me for a cup of coffee and we chatted about the script. He responded to it and amazingly agreed to be in the movie. Once Paul Rudd says he’s going to be in your movie then everything happens. Pretty much everyone with a pulse then wants to be in your movie because everyone want to act next to Paul Rudd and I don’t blame them. The nuances that he rides through with Ben being vulnerable and strong at the same time in incredible.

What about Craig Roberts? How did you know he was Trevor?

We honestly considered 250 kids with this role. I was a huge fan of “Submarine” and Paul did a chemistry read with three of four of the kids, but when we saw Paul and Craig together, that’s when we knew we had something special. This movie rises or falls based on that chemistry, so if we didn’t have what they have, there’s no movie here.

You used to be a producer on “Late Show With David Letterman,” how did you transition into a director?

I credit that show to a lot of my creative formation over the years. I think as head writer of that show is a pretty nice boot camp that helps you in the directing world. You’re dealing with a lot of departments and it’s very pressured and you have to collaborate to create a vision so there are a lot of similarity there. From the “Late Show” I worked on a show called “Ed” on NBC that I created with Jon Beckerman. There I really cut my directing chops. These were one-hour scripted television, we shot of film. It really was like making a small movie each week. It was just a natural extension for me to going from writing to then heading into a full-length feature film, it felt like a natural progression for me.