A brilliant all-round bowling display saw Birmingham Bears bowl Lancashire Lightning out for 102 as the hosts sealed a vital seven-wicket victory in the Vitality Blast at Edgbaston.
Ian Bell, the leading run-scorer in the tournament, struck 34 as the Bears chased down their target to keep last year's runners-up in contention to reach the quarter-finals.
The loss for Lancashire means Durham have secured a home last-eight clash in the North Group and although the Red Rose side remain in second they will have wait until Friday to see if the Bears can beat Worcestershire to stop the Rapids from finishing in the top two.
Birmingham sit a point behind holders Nottinghamshire Outlaws, who have 14 points and currently occupy the final quarter-final qualification spot with a game to go.
Having opted to bat first, the visitors lost both openers to Oliver Hannon-Dalby as the Warwickshire seamer used the skiddy pitch to his advantage.
Sam Hain's bobbled catch in the deep saw the end of Lancashire captain Dane Vilas for just five before Birmingham skipper Grant Elliott chipped in with 2-23 as the away side collapsed to 59-6.
A counter-attacking 24 from Danny Lamb provided a brief respite for the Lightning but Jeetan Patel (1-15) and Hannon-Dalby (4-20) wrapped up the tail as Lancashire were bowled out for a measly 102 in 19 overs.
In reply, Bell and Ed Pollock shared a 68-run first-wicket partnership - with the latter striking Arron Lilley for three consecutive sixes before falling to spinner Zahir Khan for 36.
Matt Parkinson picked up 2-16, with Bell dismissed for 34 and Adam Hose brilliantly stumped by Vilas for 10 but Colin de Grandhomme kept a cool head to ease Birmingham home in 14.1 overs.
In the South Group, Aaron Finch's unbeaten half-century eased Surrey to a seven-wicket win over Hampshire to keep alive their chances of reaching the quarter-finals.
The visitors managed just 11 boundaries in their innings with Sam Northeast's 37 Hampshire's top score as they hit a below-par 133-7.
Although Jason Roy was bowled for a first-ball duck by spinner Mujeeb Ur Rahman, Finch (67 not out) and Nic Maddinson (41 off 30 balls) saw the hosts home in 17.3 overs.
Surrey and Glamorgan, who both have one game left, are separated by a point, with the Welsh side currently in fourth with 15 points. Kent sit in third with 16 points but have two matches remaining.