The Ireland wicket-keeper hit five fours and one maximum in an unbroken fourth wicket partnership of 69 with New Zealand international Grant Elliott to see the Foxes home in front of a delighted crowd of close to 5,000 at Grace Road.
Leicestershire skipper Mark Cosgrove chose to bowl first after winning the toss, and Derbyshire suffered an early blow when Hashim Amla was held by Rob Taylor off the bowling of Clint McKay for just eight, an outstanding catch two-handed low down running in from the deep square leg boundary.
Wes Durston and Chesney Hughes took the Falcons score past 50, but Foxes’ off-spinner Jigar Naik picked up the wickets of Shiv Thakor and then Scott Elstone, both caught behind by O’Brien, off consecutive deliveries.
Tom Poynton also fell to the off-spinner, held by Tom Wells at long-on, but Hughes, improvising cleverly in between clubbing blows over the leg-side, went to his 50, though not before he was dropped by Clint McKay, the Australian failing to hold a skier off his own bowling in an incident that saw an angry Ned Eckersley confront non-striker Billy Godleman, accusing the Derbyshire batsman of shouting an inappropriate comment while the ball was in the air.
A target of just over eight runs an over allowed Leicestershire to pace their reply, and although Cosgrove went quickly, lofting Ben Cotton straight to Amla at mid-off, Eckersley hit 39 off 33 balls in a partnership of 66 with Kevin O’Brien.His dismissal brought Elliott to the wicket, and despite the increasingly bad light, Leicestershire’s overseas signing played with calm assurance. After Kevin O’Brien holed to Greg Cork at backward square leg, his older brother played himself in before striking Mark Footitt high back over his head for a huge straight six.