"It was just common sense who did it," De Niro said. "It could have gone either way for me if he didn't do it."
The question might have been why do it at all. Implausible at best, the tale of two 60-something former light heavyweight champions coming out of retirement to fight each other in an HBO pay-per-view event is a stretch even by Hollywood standards.
It wouldn't work as a drama like "Raging Bull'" or any of the six "Rocky" movies. But "Grudge Match" excels as comedy, with enough laugh-out-loud moments and good cheer to put it in the early running for the feel-good movie of the holiday season.
Grudgement Day anyone?
"I haven't been very lucky in comedy," Stallone said. "But I'm taking a character that got me here so it didn't take a lot of persuasion."
That character, of course, is Rocky Balboa, first seen in the original "Rocky" movie in 1976 and reprised in various forms five times since. The last was "Rocky Balboa" in 2006 in which the fighter comes out of retirement to take on champion Mason Dixon for the heavyweight title.
The story line for that film was similar, including the HBO pay-per-view that Rocky barely loses in a brutal fight. The difference this time is "Grudge Match" is more or less a parody, played mostly for laughs.
Instead of a tearful scene at a cemetery there's Stallone and De Niro butchering the national anthem at a monster truck event. Instead of an inspirational talk from the corner, there's trainer Alan Arkin urging Stallone's Henry "Razor" Sharp to toughen up his hands by dipping them in horse urine.
And then there's a postscript to the ending featuring a couple of real fighters who show some comedic chops of their own.
What is somewhat the same is De Niro and Stallone had to trade punches, something that can be a bit dicey for actor/boxers in their 30s, much less late 60s. Stallone drew on his choreography from the Rocky movies for the fight scenes, which come across realistic enough as long as you suspend disbelief for a few moments and accept the premise two senior citizens can still fight.
"There are thousands and thousands of punch combinations that have been practiced in films," Stallone said in a phone interview with The Associated Press. "Some work and some don't. I brought things that worked in six Rocky's and made them age appropriate. I knew it would have the desired results."
It helped that De Niro had experience in staging fights from "Raging Bull." Thankfully, he didn't have the liver punch that Mr. T threw during filming of "Rocky III" that left Stallone writhing in pain on the canvas.
"There were some close calls, some nicks in this film, that I could see on playback," Stallone said. "Your adrenaline is up, you're in front of the crowd and you're not tuned into your own body. It was sort of like just being in the moment of a fight."
The fight takes place in Pittsburgh, where Stallone's character works in a factory after losing all his money in early retirement. De Niro's Billy "The Kid" McDonnen is better off with a used car lot and bar but he still yearns for the one thing that was taken away from him — a chance to beat his hated rival in the rubber match after splitting two fights 30 years earlier.
And, of course, there's a love interest, played by the still spectacular Kim Basinger, along with a cute 6-year-old old who steals a scene or two. The fight promoter (Kevin Hart) steals a few of his own, too.
"I think this is a family movie," Stallone said. "It's like 'Meet the Fockers,' something that everyone will enjoy the ride. It's not just for Grandma."
In the end, as in all boxing movies, there's a climactic fight scene, though in this case it's hard to figure out for whom to root. Win, lose or draw something had to be settled the only way boxers know how to settle things — in the ring.
They did, something that should make old geezers everywhere feel a little better about themselves.
"It could go three ways and I would be satisfied," Stallone said. "Believe me, even in 'Rocky' when Rocky lost I was satisfied."
"Yeah," said De Niro. "Same for me."