Essex Eagles blew Group B wide open after a crushing six-wicket win over Durham Dynamos in the Yorkshire Bank 40 clash at Chelmsford.
Graham Napier took five wickets as the visitors were dismissed for just 138 and Essex made light work of the chase, reaching the total with 13.3 overs to spare.
The result knocked the Dynamos off the top of the group and left the top four separated by just three points.
Durham elected to bat after winning the toss but floundered against a wonderful exhibition of pace bowling from Napier.
The Essex all-rounder took 5-21 in 6.1 overs, including a devastating spell of four wickets for one run in 2.2 overs at the start of the innings as the the Dynamos' first four wickets fell for just nine runs.
Mark Stoneman, Scott Borthwick and Paul Collingwood all failed to score as Napier ran amok. He removed Stoneman, who was caught at midwicket, with his second delivery of the match and three balls later found the edge as Borthwick pushed forward to give James Foster one of his three catches.
Collingwood failed to dig out a perfect yorker and Phil Mustard had reached nine when he became another victim.
Will Smith offered some resistance with a 73-ball half-century and he found useful support from Gareth Breese, the pair adding 55 for the seventh wicket.
Breese then opted for a reverse sweep and was bowled by Ryan ten Doeschate and soon after Smith drove Tymal Mills to Bopara at mid-off, as Durham's innings ending as ignominiously as it had started with the loss of three wickets for one run.
Bowled out for 138 in 34.1 overs, the visitors did have some early impetus when Essex started their reply capturing three wickets for 30 runs in 11 overs.
But ten Doeschate and Ravi Bopara added a fourth wicket partnership of 94 in 18 overs to steady matters.
When Bopara became a second scalp for Rushworth, only 15 more runs were required and ten Doeschate completed his side's emphatic victory with an unbeaten 74 spanning 64 balls, with two sixes and eight fours.