2004 Explorer Mileage dropped recently

I recently found my gas mileage to have an immediate drop. Approx -5mpg on highway (20 to 15) and approx -3mpg city (15 to 12). Read up on bearing problems, so took to mechanic. No bearing problems, but rotars and brake pads replaced. Also Checked 4wd, emergency brake, tires. No issues found,no real improvement in gas mileage. Feels to have a drag of some kind.