Leicestershire 228 for 8 (Cosgrove 81*, Davis 4-60) trail Derbyshire 307 (Hosein 83*, A Hughes 55, Shreck 4-78) v Leicestershire by 79 runs
Mark Cosgrove defied the pain of a damaged hand to hold Leicestershire together but a late burst from Will Davis gave Derbyshire the edge before bad light ended play early on the second day of the Division Two game at Derby.
The Leicestershire captain was forced to retire hurt on 77 but returned and was unbeaten on 81 but Davis took three wickets in two overs to reduce the visitors to 228 for 8, 79 behind.
Derbyshire had earlier been bowled out for 307 with Harvey Hosein unbeaten on 83 as Charlie Shreck took 4 for 78, but Davis claimed 4 for 60 to tilt the balance towards the home side.
The fast bowler said: "I think we bowled well all day, there were times when wickets were harder to come by but I think we got our reward for a full day's work.
"We worked hard in the afternoon session and we all noticed the opportunity to try and make the most of the unfortunate injury so that gave us a bit of a lift and worked well for us.
"Hopefully we can finish them off quickly and I think any sort of lead will be good and will put us in the driving seat."
All the attention at the start was on Hosein who had a good chance of a maiden first-class hundred but the 19-year-old's inexperience showed as he took singles at the start of overs and scored only four more runs before Shreck wrapped up the innings.
Davis drove Shreck over extra cover for four to secure a third batting point before fending a short ball to short leg but he was soon celebrating as Leicestershire lost wickets cheaply before lunch.
Tony Palladino swung one back into Angus Robson who was struck in front but Paul Horton was tempted into flashing at a ball from Davis he should have left alone.
Neil Dexter was lucky to escape when he miscued a hook but he played another rash stroke at the first ball of the last over of the morning and was well caught at slip by Wayne Madsen.
It was just as well for Leicestershire that Cosgrove was showing greater selectivity and Ned Eckersley also played with restraint to rebuild the innings after lunch.
Derbyshire plugged away around off stump and gave little away although Cosgrove did come down the pitch to dispatch Parkinson over long on for six and a cover drive off Davis took him to 50.
Eckersley had scored two hundreds against Derbyshire at Leicester last month but he faced 92 balls for his 27 before Palladino cut one back to have him lbw.
Cosgrove had taken several blows on his injured left hand and he was finally forced to leave the field three overs later, which gave Derbyshire two new batsmen to bowl at, but Harry Dearden played well on his senior debut and dug in for 14 overs before he was caught behind pushing at Parkinson.
Clint McKay hoisted Parkinson onto the pavilion roof, breaking a tile, but the innings unravelled as Davis took three wickets with short balls in two overs.
Alex Hughes held two smart catches at deep midwicket either side of Cosgrove's return and after a top edged hook from Rob Sayer was taken at backward square, the umpires decided the light was too poor for play to continue.