The 42-year-old victim was standing on a Blue Line platform in the 200-block of North LaSalle Street at about 2:23 a.m. when police said a male suspect approached him and demanded money.
Police said the suspect struck the victim in the face and took his wallet before fleeing on the train.
The victim was transported to Northwestern Memorial Hospital in good condition with a laceration to the nose.
Area One detectives are investigating.
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