The deliveryman robber apparently struck for the fourth straight day late Saturday – this time on the Upper West Side.

Police believe the same man robbed three food deliverymen on the Upper East Side last week.

On Saturday, the man called up Big Nick’s on 71st Street and Columbus Avenue at about 8:50 p.m. and placed an order that included his food of choice: grilled chicken. As has been his habit, he asked that the deliveryman come with change for a $100 bill. When the 40-year-old deliveryman arrived, he realized there was no apartment 3A at 115th W. 85th St. There was a voice coming from down the hall, speaking in Spanish.

“The food is mine,” the man said, according to police. He motioned for the deliveryman, Juan, to follow him into the basement.

When Juan held out the food, the man pulled out a knife. He ordered Juan to strip naked and lay on the floor in a corner of the abandoned basement. He took $250 in cash, the food, and the keys to Juan’s bicycle lock, police said. He scattered the clothes in the hallway.

Yesterday evening, Juan didn’t come back to work, the night manager at Big Nick’s said.

“I don’t know if he’s coming back,” he said. “He got scared.”

Police said they believe the same man has hit up fast food restaurants every day since Wednesday, each time using the same tactic. At least one other deliveryman may have quit his job after the harrowing experience.

The owner of Frankie’s and Mocca, a Hungarian-American restaurant on Second Avenue and 81st Street, Tarek Soliman, said his deliveryman hadn’t come back after being robbed on Thursday at about 5 p.m. The robber ordered coffee, chicken with stuffing, and chocolate cake – and asked to pay with a $100 bill. When the deliveryman arrived, he was called up to an abandoned apartment on the fifth floor, where he was robbed of the food, $82, and his bicycle.

Like Juan from Big Nick’s, the bicycle was his own.

Two of the robberies occurred at 331 E. 81st St., the superintendent of the building, August Pollio Jr., said he thought the man had some kind of skeleton key that helped him get into buildings and apartments. The door to the apartment was locked the last time he checked, he said. Tenants of the building said the front door had a weak lock.

A deliveryman from Chirping Chicken on 85th Street and Lexington Avenue, Carlos Gregorio, 22, said the robber was so quick he barely realized what happened.

“With his left hand he took the receipt, and with his right he put a knife to my throat,” Mr. Gregorio said through an interpreter.

The man took about $250, an order of chicken, and his bicycle.

A deliveryman from Ritz Diner on 62nd Street and First Avenue was robbed on Wednesday.