Hardus Viljoen took 4-51 as Derbyshire fought back late on Day Three to leave the game finely poised heading into the final day away to Northamptonshire.
The tall quick was the pick of the bowlers, while Ravi Rampaul claimed three wickets to leave the hosts on 198-8 at the close.
Leading by 231 runs with two wickets in hand, Derbyshire will be aiming to dismiss the tail early in the morning session to set up a competitive chase at Wantage Road.
Four-day cricket is back! Derbyshire host their final Specsavers County Championship match of the season against Gloucestershire from Monday 24 September. Buy your tickets in advance and save.