Derbyshire 57 for 0 (Reece 26*, Godleman 25*) trail Leicestershire 249 (Scriven 53, Conners 5-51) by 192 runs
England Lions fast bowler Sam Conners returned his best Championship figures of the season as Derbyshire made the early running on the opening day of the LV=Insurance match against Leicestershire at Derby.
Conners took 5 for 51 and pace partner Ben Aitchison 3 for 46 to bowl Leicestershire out for 249 with all-rounder Tom Scriven scoring 53, his third first-class half-century.
When bad light ended play three overs early, Derbyshire openers Billy Godleman and Luis Reece had moved to 57 without loss, 192 behind.
Derbyshire's decision to bowl first was influenced by a green tinge to the pitch and threatening cloud cover but initially, they failed to exploit the conditions.
Aitchison was inconsistent in his opening spell and Nick Potts served up too many loose deliveries which allowed Sol Budinger and Sam Evans early momentum.
Leicestershire were going well until Budinger top-edged a pull at Aitchison and Brooke Guest leapt to take an excellent catch above his head.
The introduction of Conners and Anuj Dal slowed the scoring rate and the pressure was rewarded when Evans pushed at a ball he could have left and Guest pouched his second victim.
Even so, Leicestershire were still well placed at lunch on 90 for 2 but the frailty of their batting was again exposed as four wickets went down in an afternoon session shortened by rain.
Louis Kimber was bowled by one from Aitchison that straightened and Lewis Hill followed six overs later, caught low down at first slip as he played forward.
Rehan Ahmed and Harry Swindells added 41 in 10 overs before Conners struck twice in three balls with Ahmed bowled aiming to drive and Swindells getting a leading edge as he looked to work the ball through midwicket.
But Derbyshire were frustrated by Scriven who played the best innings of the day to take his side past 200. He launched Alex Thomson over wide long-on for six and completed a deserved fifty when he steered Conners wide of third man for his sixth four.
By then, Roman Walker had clipped Thomson into Dal's hands at midwicket and Conners wrapped up the innings in the space of four balls as Leicestershire fell one short of a second batting point.
Scrivens was lbw as he tried to work the fast bowler to leg and Callum Parkinson could only edge one that left him to give Guest his 50th championship catch of the season, the first Derbyshire wicketkeeper to reach the milestone since Luke Sutton in 2011.
Derbyshire were left with 19 overs to bat and their reply started to the surreal backdrop of fireworks exploding in bright sunshine above the City End of the Incora County Ground.
There were no batting pyrotechnics as Godleman and Reece accumulated steadily to the close although Reece was given a reprieve on 10 when he edged Scriven to third slip where Budinger spilled the chance.