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Paul Walker -- and his Fast & Furious character, Brian O'Connor -- was irreplaceable. So it comes as no surprise that, in the wake of the actor's tragic death last November in a car accident, planned April 2015 sequel Fast & Furious 7 apparently remains in turmoil - with screenwriters scrambling to rework the script.

Just ask Kurt Russell, who was cast as a "father figure" to Brian O'Connor in the upcoming installment of the blockbuster franchise. Promoting documentary The Battered Bastards of Baseball at the Sundance Film Festival, Russell, 62, was frank with reporters about reworking FF7 without Walker, who had only just begun shooting scenes before he passed away Nov. 30 at age 41.

"They're having to rewrite, they're having to do whatever they're having to do to deal with the situation," Russell said, according to BBC. "It's catastrophic. It's the worst thing that could happen to a movie," the veteran actor added before qualifying, "but it's not as bad as what happened to Paul."

"So everything is in perspective," continued Goldie Hawn's love of over 30 years. "He was a terrific guy. And life is full of curveballs.It's just a situation that they'll work out and, at that time, I'll go back to work."

As it happens, Russell only had "one day left" of shooting before Walker's passing. "I don't know what is going to happen with that. It's obviously a difficult situation." He added that the fate of Brian O'Connor's character remains unknown.

"Whether or not this guy dies off in the movie, we don't know. That may have changed now significantly too."

Russell's participation in FF7 was first revealed by series mainstay Vin Diesel, who shared a set photo that included the action star flanked by Walker and Russell.