Derbyshire realistically ended Durham's hopes of reaching the Yorkshire Bank 40 semi-finals with a crushing 107-run win in their televised Group B clash.
Needing a victory to remain in the qualification race, the Dynamos were bowled out for a mere 110 inside 29 overs in reply to the home side's total of 217-8.
Wayne Madsen made 37 with the bat but it was with the ball that he made his most telling contribution, claiming 3-27 - his best figures in any form of cricket - on a slow, turning pitch at Derby.
David Wainwright made sure Durham never recovered from 62-4, the left-arm spinner taking a limited-overs career-best 4-11 to help Derbyshire end a run of four defeats to their opponents from the north east this season.
The Derbyshire captain was rewarded for his decision to open the bowling himself, striking twice with his part-time spin in a five-over spell that cost only 13 runs.
Paul Collingwood and Mark Stoneman added 46 in nine overs for Durham before Madsen returned to get the latter caught at long off for 25.
Tom Knight's left-arm spin accounted for Collingwood (24), as well as the dangerous Ben Stokes, and then Wainwright ended the match in a hurry, Durham's last four wickets falling for just nine runs.
The visitors - without the injured Graham Onions - will look back at their failure to make the most of a good start with the ball, allowing Derbyshire to recover from 36-3.
Richard Johnson made the most of being caught behind off a no ball from Stokes when on 17 to make a top score of 58, combining with his skipper Madsen to add 103 from 114 balls for the fourth wicket.
Tony Palladino weighed in with 22 from only 15 deliveries in the closing stages while 25 extras helped lift Derbyshire to a total that always looked challenging considering the nature of the surface.