The accident happened just as the doors were closing on the platform in Syosset, Long Island.
A passenger tumbled into a huge gap and onto the rail bed after witnesses said he suddenly bolted off the train.
Moments later the conductor was maintaining contact with the man as Syosset firefighters devised a plan to pull him out from beneath the platform.
Passengers watched from inside the train as the victim was carried out of the rail bed and onto a stretcher.
The man in his 70s suffered a cut to his head. He was taken to Syosset Hospital for treatment.
Service on the Port Jefferson Branch was shut down for 25 minutes, until the man was pulled to the street and third rail power was restored.
It was nearly four years ago that a teenager was killed after falling through a similar gap in Woodside, Queens. The LIRR later acknowledged hundreds of gap accidents since 1995 and pledged to make repairs.