Michael Jones, 25, of West Harrison, N.Y., was walking near Union Square in Manhattan when he was slashed in the neck and torso by the man, the New York Daily News reported Monday.
Jones, originally from Liverpool, England, was a part-time coach in the Red Bulls' training program, instructing local third-graders, among others.
A surveillance video of the area showed Jones walking with his assailant when the argument and attack occurred, police said.
A passerby alerted a firefighter, the newspaper said.
"He told them you better get down here, someone got their throat cut," said Malachi Mohamed, 39, who witnessed the incident.
Jones was pronounced dead at Bellevue Hospital.