Durham shrugged off another injury to skipper Paul Collingwood to boost their chances of reaching a second quarter-final when they beat Yorkshire by 15 runs at Emirates Riverside.
After both teams progressed in the NatWest T20 Blast on Friday, both can also reach the last eight in the Royal London Cup by winning their final group matches tomorrow.
Durham go to Old Trafford and Yorkshire entertain Warwickshire but will hope to bat better than in attempting to chase down Durham’s 281 for seven.
At 200-5 after 40 overs they were 16 ahead of Durham at the equivalent stage, but despite Tim Bresnan continuing his fine batting form with 92 the boundaries dried up against tight bowling.
Only 38 runs came off the next seven overs and there had not been a boundary for 12 overs until Bresnan twice planted Chris Rushworth into the stand over mid-wicket in the 48th.
He than holed out off the last ball of the over, leaving 28 needed off two with two wickets standing. Mark Wood conceded only one run in the 49th and Yorkshire finished on 266 for eight.
Collingwood, who took over the one-day captaincy from the departing Mark Stoneman last week, was limping while batting and in his absence from the field Keaton Jennings took over.
He skilfully marshalled an excellent bowling display, led by Wood after he was belatedly made available as he continues his comeback from two ankle operations.
He took the crucial wickets of Alex Lees and Jack Leaning while conceding only 43 runs in ten overs.
Scott Borthwick was Durham’s star, top-scoring with 84 and taking one for 48 in ten overs of generally tight leg spin, spoilt only when Bresnan drove a full toss for six then pulled a long hop for four.
That came towards the end of a fifth-wicket stand of 76 with Jack Leaning, but when Wood was recalled Leaning steered a catch straight to backward point and the momentum was never recovered.
Borthwick accelerated nicely from a 74-ball half-century to reach 84 before breaking his bat, only to fall without addition when the new blade sent a miscued hook to long leg in the 41st over.
Durham did well to take 97 off their last ten overs as, despite hitting only two boundaries, Michael Richardson kept the score moving with 53 off 58 balls.
He was helped in the last ten overs by cameos from Ryan Pringle, with 27 off 20 balls, and Stuart Poynter, who included a straight six off Bresnan in his unbeaten 27.