Northampton pushed their Championship opponents all the way, losing only to a Johnny Russell goal in the first-half as Chris Wilder's side played the first of two home friendlies in four days.
Clement told the official DCFC website that 'we were really poor in the first half and marginally better in the second,' as the new man in charge of the Rams looks to put his stamp on a squad that tailed away from the promotion places in the latter part of last season.
For the Cobblers, Birmingham City are next at Sixfields on Tuesday evening.