The Godfather of “granny” free throws has a proposal for Mitchell Robinson: Let me fix your problem.

NBA Hall of Famer Rick Barry observed Robinson’s struggles on Saturday and, though frustrated, believes he can transform the Knicks center into a 75 percent free-throw shooter if he adopted the underhand technique.

“It’s baffling. It’s unfortunate that players struggle with the simplest part of basketball—the only aspect without any defense,” Barry remarked during an interview with The Post. “It defies logic. Free throws are crucial in the game. It’s disappointing. I think he’s a prime candidate for shooting underhand. He needs a change. You can’t continue with 30 or 40 percent shooting.”

Currently, Robinson is hitting only 29 percent of his free throws during the playoffs, which has led to Boston exploiting him with the “Hack-a-Mitch” tactic. In Game 3 on Saturday, Robinson managed to sink four out of his 12 attempts and played only 19 minutes, despite his otherwise strong rebounding performance for the Knicks.