Renée Zellweger inChicago(2002).Photo: Miramax/Courtesy Everett Collection

Given herOscar-nominated performance inChicago, fans would likely never suspectRenée Zellwegerhad any insecurities about playing murderess-turned-famous-showgirl Roxie Hart.
But in a new interview surrounding themusicalfilm’s 20th anniversary, director Rob Marshall toldThe Hollywood Reporterthat initially, Zellweger “was very afraid to sing” for him.
“We went to dinner, and I said to her, ‘Do you know any songs?’ " Marshall, 62, recalled with a laugh. “And she started singing ‘Diamonds Are a Girl’s Best Friend’ for me in the restaurant becauseshe was so shy about singingformally. I could tell immediately she could sing.”
Zellweger, 53, was “exactly the actor” Marshall “was looking for,” as his goal was “to find a vulnerable Roxie,someone who could play the fragile partof her, but then also be a good enough actress to turn the tables and become the strong killer that she becomes, and it needed that full range.”
“I’d found out that Renée had been a cheerleader in school, so I thought maybe she could dance,” he toldTHR. “She came to New York, and [choreography supervisor] John DeLuca and I worked with her on dancing and could see right away that she could move.”
Never miss a story — sign up forPEOPLE’s free daily newsletterto stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human-interest stories.
Marshall also revealed that there “had been talk” over the years about who they might want to appear in the film, includingMadonna,Goldie Hawn,John TravoltaandLiza Minnelli.
According to the director,Catherine Zeta-Jones, who starred inChicagoas Roxie’s fellow murderess and nemesis-turned-collaborator Velma Kelly, “was the easiest to cast because she had very clear musical chops, having played in West End musicals.”
“Richard Gerehad doneGreaseand played Danny Zuko, so I knew he had musical talent,” Marshall added of the actor who would go on to play silver-tongued attorney Billy Flynn.
And while he also spoke toKevin KlineandKevin Spaceyabout the role, “It was very clear to me that Richard was the one,” Marshall said.
“In a perfect world, you don’t even have to make a decision about actors,” he added. “The actor themselves, if they’re right for the role, they claim it as theirs, and that’s what Richard Gere did.”
Catherine Zeta-Jones and Renée Zellweger inChicago(2002).Mary Evans/MIRAMAX/Ronald Grant/Everett Collection

Chicagoearned 13 nominations at the75th Academy Awards, including winsfor Best Picture, Best Art Direction, Best Costume Design, Best Film Editing, Best Sound and Best Supporting Actress for Zeta-Jones.
BothJohn C. ReillyandQueen Latifahwere also nominated in the Best Supporting Actor and Supporting Actress categories for their roles as Amos Hart and Matron “Mama” Morton, respectively.
source: people.com