An off-duty NYPD chief helped nab to hapless crooks who tried to rob a Staten Island gas station early yesterday, The Post has learned.

Chief Michael Scagnelli, 59, who heads up the department’s Transportation Bureau, sprang into action after he was flagged down by a frightened gas station attendant at the corner of Hylan Boulevard and Nelson Avenue in Eltingville at 4:00 a.m., cops said.

The attendant at Pegasus Automotive told the 36-year NYPD veteran that two men in a Silver Honda circled the gas pumps three times before they finally stopped, simulated a gun and demanded cash, police sources said.

When the worker would not comply, Joseph Morigi, 40, allegedly punched him in the face, ran into the station office and fled a few moments later.

That’s when the attendant ran into the street and spotted Scagnelli – who immediately followed Morigi and his alleged accomplice Peter Gurin, 26, to Tarlee Place and Florence Street, police sources said.