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Hulk Hogan 's widow, Sky Daily , is "planning" to file a lawsuit against at least one of the WWE legend's doctors and others for medical malpractice she says led to his death, sources with direct knowledge tell TMZ Sports .

The suit, we're told, would center around the neck operation Hulk underwent back in May. Gallery Launch Gallery

Sky first told us ... she believes Hogan's phrenic nerve -- which controls your breathing -- was "compromised" during that procedure.

Those issues are thought to have played a significant role in his ultimate demise at his Clearwater Beach, Fla. home on July 24 ... as sources who have heard the 911 audio tell us Sky informed authorities on the emergency call, "My husband's not breathing. H

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