While NSW Police did not identify the victim, described as a 50-year-old man, MacGill was quickly named by multiple media outlets.
The alleged victim was confronted by a man at Cremorne on Sydney's north shore at 8pm on April 14, police said.
Then two other men arrived and helped force him into a car before driving him to Bringelly, in Sydney's southwest, where he was threatened with a firearm.
An hour later the victim was driven to Belmore and released.
The incident was reported to police on April 20 and four men - aged 27, 29, 42 and 46 - were arrested in dawn raids on Wednesday.
The men have been taken to police stations where charges are expected to be laid.
Police officers are in the process of executing search warrants at homes at Sutherland, Caringbah, Brighton Le-Sands, Banksia and Marrickville.
MacGill played 44 Tests for Australia between 1998 and 2008.