Durham left Yorkshire’s Vitality Blast hopes hanging by the thinnest of threads by defending 148 to win by 43 runs at Emerald Headingley.
The Vikings are not mathematically out of contention – four points behind second-placed Lancashire and one behind Durham in third – but they must win their last two North Group fixtures and hope for other results to go their way.
Yorkshire’s third successive defeat came in a fixture which saw both sides struggle with the bat.
Durham were 40-0 after four overs, only to be bowled out for 147.
Yorkshire then slipped to 73-6 in the 11th over of their chase and lost with 20 balls remaining, with new ball seamer Matty Potts claiming 3-14 from three overs.
Yorkshire’s South African Duanne Olivier impressed for 2-16 from four overs in his first Blast outing of the summer after Adam Lyth had elected to bowl first.
The big quick was selected in place of Mat Pillans, the only change from Monday’s Roses defeat.
That means Matthew Fisher, Tom Kohler-Cadmore, Josh Poysden and captain David Willey remained unavailable in accordance with Coronavirus guidelines, and they will be for the rest of the group stage.
Willey and his wife Carolynne have tested positive, and all players have to self isolate for 14 days as a result having met up away from cricket on Saturday.
On the field, Graham Clark’s brisk 28 – the top score in the innings – got Durham off to a flyer.
But Olivier was central to the fightback, as were Adam Lyth and Jordan Thompson with two wickets apiece and the excellent Jack Shutt with one.
Unfortunately, though, the wickets continued to tumble in the Vikings reply, with them losing Lyth, Dawid Malan – for a golden duck – and Harry Brook cheaply inside the first four overs as the score fell to 22-3.
Clark and opening partner Alex Lees fell within two overs of each other – Lees caught and bowled by Lyth’s off-spin and Clark caught at long-on off the same bowler as the score fell to 57-2 in the eighth.
Ben Raine (23) ended the eighth over with successive leg-side sixes against Lyth, but runs were to be at a premium as the hosts applied the squeeze.
Jack Shutt got him caught behind cutting – 78-3 in the 10th over – as the off-spinner returned an excellent 1-24 from four.
Farhaan Behardien then dragged compatriot Olivier to mid-on in the 11th before David Bedingham was caught at deep mid-wicket off Thompson’s seamers (94-5 after 13 overs).
Brydon Carse (22) counter-punched with a couple of lusty sixes down the ground off Shutt and Thompson, only to be caught behind the ball after hitting the second six as the score fell to 110-6 after 15.
And Olivier returned to brilliantly finish his spell by getting Paul Coughlin caught at mid-off in the 18th.
Liam Trevaskis was run out in the 19th, in which Ben Coad also had Matty Potts caught at long-on (135-9). Scott Steel was also run out in the last over to wrap up the innings.
However, Yorkshire were about to encounter batting issues of their own.
Seamer Potts removed Lyth and Brook caught at mid-on and Malan bowled via an inside-edge. The wickets of Lyth and Malan fell to consecutive deliveries.
Jonny Tattersall was later trapped lbw by Nathan Rimmington – 48-4 in the seventh – before Will Fraine and George Hill calmed things down.
Fraine top-scored with 28, only for him and Hill to fall in successive deliveries in the 10th and 11th overs, leaving the score at 73-6.
Hill was bowled by Coughlin and Fraine caught behind off Carse.
The end came very quickly from there as James Wharton chipped Coughlin to cover. The same bowler later got Thompson caught in the deep.
Either side of the Thompson wicket, Trevaskis had Coad stumped and Olivier bowled, sealing the two points for the visitors.