Leicestershire 149 for 7 beat Derbyshire 94 by 55 runs
Leicestershire put themselves firmly in the chase for the Vitality Blast quarter finals when they thrashed Derbyshire by 55 runs at Derby.
The unpredictable North Group sprung another surprise when the Falcons collapsed dramatically chasing what looked a modest target of 150.
There were signs of what was to come when, after starting steadily, the Foxes began to unravel once they tried to accelerate on a used pitch with three wickets falling in five overs.
Cosgrove drove Alex Hughes for consecutive fours but Lilley sliced a cut at Luis Reece to point and Cosgrove's attempt to disrupt Critchley's line only ended in the hands of deep mid-wicket.
Harry Dearden lifted Hughes over deep square for six but then drove to long off and when Ackermann was well caught by Reece diving forward at backward square in the 15th over, the Foxes had slipped to 106 for 5.
The Falcons bowled with discipline on a pitch where the ball was not coming on and, backed up by smart fielding, did not allow the Foxes to break free and only 72 came from the last 10 overs.
Aadil Ali drove Hughes for six and Callum Parkinson hit the last two balls of the innings from Rampaul for four but the Foxes total seemed below par until the Falcons top order disintegrated in the powerplay.
Luis Reece sliced to point after pulling a ball into his helmet and although Wayne Madsen swung a free hit from Dieter Klein for six, he top-edged a reverse sweep at Ackermann and was caught at short third man.
It got even worse for the home side in the third over as Billy Godleman sliced Griffiths to third man and Leus du Plooy pulled the next ball into the hands of deep square leg.
Former Fox Darren Stevens was run out by Ackermann's direct hit from cover when he failed to ground his bat and when Hughes swung another short ball to deep mid-wicket, the Falcons were in free-fall.
Fynn Hudson-Prentice drove Parkinson for six but the former Derbyshire spinner responded by yorking Matt Critchley and the only consolation for the Falcons was they passed their previous lowest T20 score of 72, against the Foxes six years ago.