O.J. Simpson thinks the rusty buck knife found on his former Brentwood estate has nothing to do with the murder of his ex-wife Nicole Brown Simpson and her friend Ron Goldman.

“O.J. has a saying,” retired prison guard Jeffrey Felix, who befriended Simpson in Nevada’s Lovelock Correctional Center, told The New York Post. “ ‘If the knife is rusted, I can’t be busted.’”

It’s a play on his lawyer Johnnie Cochran’s famous line, “If [the glove] doesn’t fit, you must acquit.”

“He thinks it’s a total joke,” Felix — author of “Guarding the Juice,” in bookstores next Wednesday — said. “O.J. is laughing about it. He’s on top of his game. He’s like Muhammad Ali.”

“He says almost every construction worker carries one of those folding knives. Anyone could have dropped it.”

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