Goals from Marcus Joseph, Faisal Ali, Brandon Vanlalremdika and Nikola Stojanovic made sure the Black Panthers quest for a third Durand title remained on course.
Friday's quarterfinal between Army Red and Bengaluru United was called off after an Army Red player tested positive for COVID-19.
Willis Plaza scored the winner for Delhi FC.
Nigerian striker Chisom Elvis Chikatara scored a hat-trick as the holders thumped Assam Rifles 7-2.
Emil Benny was sent off shortly after Rahim Osumanu scored for the defending champions.
Blasters, who have three points from two matches, take on Delhi FC in their final group game on September 21.
Hyderabad FC thumped Assam Rifles 5-0 in another Group D match.
Uruguayan midfielder Adrian Luna scored the winner off a penalty in the 70th minute.
The Indian Super League side will be making its debut in the prestigious football tournament.
Gokulam Kerala are the defending champions.