Diaz was hospitalized after allegedly blowing a stop sign and colliding with a fire truck at 8:17 p.m. at Cermak Road and Hoyne Avenue, said Fire Media Affairs Director Larry Langford.
The Chicago Fire Dept. truck struck by the car was responding to a fire at 23rd Street and Damen Ave., Langford said.
The fire truck was heading east on Cermak Road on its way to the fire when a man driving a Chrysler Concorde blew a stop sign on Hoyne, directly in front of the truck, Langford said.
The truck, which had its lights and siren on and was blowing its airhorn, broadsided the car which was then shoved into a light pole. The vehicle then struck two parked cars on the street, Langford said.
Diaz was taken to Mount Sinai Hospital in critical condition as a precautionary measure, but was alert and did not appear to have any serious injuries following the crash, Langford said.
Diaz was the only one in the car and the driver area did not sustain heavy damage. Langford said the passenger side of the vehicle was badly damaged.
No firefighters in the truck were injured in the crash. The crew, who were all medically trained, rendered aid to the man before ambulances could arrive, Langford said.
Police will be requesting a blood alcohol level for the driver involved in the crash once he becomes "stable" enough at the hospital to determine whether he was drinking, Langford said.
"He appeared to have been intoxicated and the crew that treated him said he definitely smelled of liquor," Langford said.
Diaz's car was totaled in the crash and remained at the scene at 9:15 p.m. Friday awaiting a tow truck.