Bryan Alexander

USA TODAY

Like many fans of Sylvester Stallone’s Oscar-nominated role as Rocky Balboa in 1976's Rocky, actor Liev Schreiber wasn't aware of a key film fact. The unknown boxer character who gets the chance of a lifetime to fight the world's heavyweight champion was inspired by an actual fighter named Chuck Wepner.

“I’m embarrassed to admit I didn’t know who Chuck was,” says Schreiber, who plays Wepner in Chuck (in theaters Friday in New York and Los Angeles, expands nationwide through May 26). “And I was blown away when I found out."

Here are five important points of comparison between the two boxers:

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Both went 15 rounds with the heavyweight champ

In Rocky, the underachieving Balboa dramatically lasts 15 rounds with overconfident champ Apollo Creed (Carl Weathers).

In 1975, Muhammad Ali fought Wepner, a little-known bruiser from Bayonne, N.J., at Cleveland Coliseum. Wepner, now 78, had earned the nickname “The Bayonne Bleeder” for his frequently bloodied face. “I had 328 stitches total. So I bled a little bit," Wepner says.

The fight was supposed to be a lark for Ali, who prepared minimally. Wepner devoted himself fully to training for the first time in his career and shocked Ali with a knockdown in the ninth round. In the 15th, a focused Ali floored Wepner and the referee called the fight.

“I showed the world that I belonged in there. That’s what I really wanted to do," says Wepner.

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That stair run was real

Balboa’s famed training run ended with a sprint up the 72 steps of the Philadelphia Museum of Art. Wepner ran the 46 steps at Bayonne’s Hudson County Park.

"The running up the stairs they used in the films, that was all my life,” Wepner says. “Everyone loved it. I loved it. Because I knew I was the real Rocky.”

Fundraising efforts are underway to erect a statue of Wepner at the top of the steps.

Drinking raw eggs? No way

Stallone’s Rocky rose at 4 a.m. for his old-school training drink of raw eggs. Wepner cringes at that stomach-upsetting thought. “If you’re drinking raw eggs when training, you better be wearing Depends,” Wepner says. He preferred getting his muscle-building protein from raw meat.

The real boxer didn't punch slabs of beef in a meat locker, as Rocky did. “I trained on punching bags in the gym and heavy people in bars," Wepner says. "I was undefeated in about 87 bar fights.”

There were no calls for ‘Adrian!’

A bloodied Rocky called out for his beloved Adrian (Talia Shire) at the end of Rocky. Wepner's then-wife Phyllis (played by Elisabeth Moss) watched the fight from a nearby hotel room.

Wepner gave Phyllis a powder-blue negligee beforehand, telling her she'd be spending the night with the heavyweight champion of the world.

"I come back to the hotel and she’s sitting on the edge of the bed in the negligee. She says, “Am I going to Ali’s room or is he coming to mine?' " Wepner recalls. "She had a sense of humor."

Wepner blew his chance to appear in 'Rocky II'

Stallone acknowledged Wepner as his Rocky inspiration and wanted to cast the boxer as a sparring partner in 1979's Rocky II. But Wepner was in a destructive cycle that would lead to his 1985 arrest for cocaine possession and nearly three years of prison time. He failed the audition.

“I was out for two days partying and showed up with a friend and a couple of go-go girls,” says Wepner, now "clean and straight" and faithfully remarried. “I just didn’t do good for the part. I deserved not to be in the movie.”