One of the selling points for Quentin Tarantino‘s Once Upon a Time in Hollywood is the big movie-star team-up of Leonardo DiCaprio and Brad Pitt. But things could’ve turned out much differently. According to Tarantino, if Brad Pitt hadn’t been available, he would’ve offered another big movie star his role: Tom Cruise. But that doesn’t mean DiCaprio would still be in the movie too. As Tarantino tells it, it was important to get the pairing of his leading men just right.

Back when casting rumors were flying around about Tarantino’s then-untitled Once Upon a Time in Hollywood, one of the big names that kept coming up was Tom Cruise. Cruise obviously isn’t in the movie now, but he could have been. Speaking with the Happy Sad Confused podcast (via The Playlist), Tarantino confirmed that he did indeed talk to Cruise about joining the film: “He’s a great guy and we really hit it off. [A collaboration] could happen on something else.”

So why didn’t Cruise make it into the film? According to Tarantino, it was all about getting the right combo of leading men. DiCaprio and Pitt, both of whom Tarantino has worked with before, were his first choices to star in Hollywood, with DiCaprio as star Rick Dalton, and Pitt as his stuntman Cliff Booth. But landing them was never a sure thing. “You can’t count on that,” the director said. “They both have to respond to it, they both have to want to play those roles, they both have to be available, there’s a whole lot of stuff there. And if you’re casting an actor, casting a team, where the one guy is a double of another guy then they have to match up in the right kind of way.”

While DiCaprio and Pitt don’t really look alike, they’re a much closer match than, say, DiCaprio and Cruise. Tarantino went on to reveal that he had several pairings in mind, should DiCaprio or Pitt not be available:

“So the reality is I had maybe eight different pairings of actors that could go together in a realistic way in this kind of situation. Now the ones that I got were definitely my number 1 [choices], but I could never just be confident about that, I had to have a few different backups and a few different exploratory ways to go.”

Tarantino doesn’t clarify who those alternates are, nor does he say who he would’ve paired Cruise up with – and I’m dying to know the answer to that. Hopefully, he’ll reveal that info someday.

Once Upon a Time in Hollywood opens July 26.