Leicestershire 152 (Ackermann 37, Parnell 4-25) beat Worcestershire 119 (Cox 30, Griffiths 3-23, Davis 3-24) by 33 runs
Leicestershire Foxes upset the form book when they toppled holders and in-form Worcestershire Rapids by 33 runs in a North Group encounter at Blackfinch New Road.
The vaunted Rapids top order were blown away in pursuit of a target of 153 as the Foxes secured only their second win of the season.
A mixture of poor batting, disciplined bowling and some sharp catching sealed victory for the Foxes and moved them off the bottom of the table as the home side were eventually dismissed for 119 in 19.2 overs.
Will Davis picked up three crucial wickets in the top six and finished with 3 for 24. He was well supported by Gavin Griffiths, who took 3 for 23, and Callum Parkinson's 2 for 21.
It ended a run of three successive victories for the Rapids which had propelled them into second spot behind Lancashire.
The Foxes were put in to bat on the wicket that had been used for the previous two Blast matches with Durham and Derbyshire.
A stunning catch by Rapids captain Callum Ferguson brought the first breakthrough in Dillon Pennington's second over as Mark Cosgrove lofted the paceman to mid on and Ferguson held onto a one-handed effort in full flight.
Pennington then held onto a smart catch of his own, running back from short fine leg and over his shoulder to dispose of Harry Swindells off Wayne Parnell.
Aaron Lilley looked in good touch and collected four boundaries from his first six deliveries as the Foxes reached 55 for 2 at the end of the Powerplay.
Lilley holed out to deep mid-wicket off Ed Barnard and Harry Dearden was caught and bowled in Daryl Mitchell's first over.
Colin Ackermann and Lewis Hill took their time in rebuilding the Foxes' innings via a partnership of 49 in seven overs. But Barnard returned to the attack to break the stand when Hill was caught at long on.
The second half of the innings was clinically disposed of by Parnell and Pat Brown. Aadil Ali was bowled by Parnell, and then Callum Parkinson and Colin Ackermann were both caught by George Rhodes in Brown's next over, the second a fine effort over his shoulder running back from cover. Parnell wrapped up the innings in clinical fashion in removing Dieter Klein and Will Davis cheaply.
But Worcestershire's big-hitting top four were blown away in the space of 12 runs. Martin Guptill reached 15, hitting Griffiths for one straight six, but in the same over he found the hands of deep mid wicket. In the next over, Riki Wessels attempted a sweep against Davis and was caught behind. Parnell miscued high into the air in the same over and presented another comfortable catch to keeper Hill.
It became 39 for 4 when Callum Ferguson also perished in the mid wicket region off Parkinson. Ross Whiteley was pouched at deep backward square to give Davis a third scalp.
Ben Cox and Barnard briefly threatened to haul the Rapids back into contention during a steady partnership of 31. But Cox was bowled for 30 attempting a paddle sweep against Ackermann and Barnard fell at deep mid wicket off Parkinson to all but end the match as a contest.