A Bronx man has been busted for pummeling an off-duty NYPD sergeant, police said.

Sherred Johnson, 31, was charged with assault in connection with the vicious March 28 attack on East 90th Street and First Avenue, the NYPD said.

Johnson was riding a motorcycle around the Upper East Side and allegedly punched the sergeant in the face and knocked him to the ground after the officer asked the reckless motorcyclist to slow down, police said.

The sergeant, 52, was walking his dog at East 90th Street and First Avenue around 7 p.m. on Tuesday when he spotted a man zooming around on a green motorcycle and asked him to go easy, authorities said. 

The request apparently enraged the biker and the two men began fighting, cops said. The biker repeatedly punched the off-duty cop in the face, causing him to crumple to the ground, police said. 

The unhinged attacker kept battering the fallen sergeant, before riding off on the bike, heading east on East 90th Street, authorities said. 

The injured cop was taken to Weill Cornell Medical Center with a broken left ankle and a cut on his right ear and lip, police sources said.