Durham 151 for 4 (Mustard 46) beat Lancashire 149 for 8 (Guptill 72, McCarthy 3-23, Arshad 3-30) by six wickets
A fine half-century on debut by Martin Guptill could not prevent cup-holders Lancashire Lightning slumping to their second successive defeat when they lost to Durham Jets by six wickets in Friday's NatWest T20 Blast game at Emirates Old Trafford.
Guptill made 72 off 46 balls but the New Zealand opener's efforts were rather eclipsed by his Jets counterpart Phil Mustard, whose 46 off 18 balls included five fours and three sixes and put his side on course to overhaul Lightning's plainly inadequate 149 for 8.
Graham Clark then took up where Mustard had left off and made 36 off 27 balls as the Jets romped home with five overs to spare.
Having been asked to bat first, Lancashire Lightning's innings got off to a poor start when they lost Alviro Petersen and Karl Brown to successive balls in Usman Arshad's second over.
Things got worse for the hosts two overs later when Arshad took his third wicket in ten balls, Jos Buttler skying the seamer on the off side only to see Paul Collingwood take a fine diving catch running back from point.
That left Lancashire on 46 for 3 but Guptill and Steven Croft repaired some of the damage with a stand of 60 in eight overs, Guptill reaching his half-century off 34 balls with a single off Scott Borthwick.
Guptill hit his only six when he deposited a Borthwick long hop over the rope in the 13th over and the pair brought up their fifty stand in the same over.
However, instead of marking the start of an acceleration, that six was the last boundary for half a dozen overs, during which Lightning lost four wickets, three of them in the same Barry McCarthy over.
The key wicket of Guptill had earlier been taken by McCarthy when the Kiwi opener pulled the Irish seamer to midwicket, where Borthwick dived backwards to take an outstanding catch. Guptill hit ten fours and a six in his innings but the other Lancashire batsmen managed just four more boundaries between them as Collingwood and Borthwick strangled the run-rate.
Indeed, there were no weak links in the Jets attack. McCarthy fully deserved his figures of 3 for 23 and Arshad, who had made the vital breakthroughs in the Powerplay overs, finished with three for 30.
A six from Neil Wagner helped hoist the score to 149 for 8 off their 20-over allotment but that total looked insufficient on a good pitch at Emirates Old Trafford.
The modesty of Lancashire's total and the limitations of the Lightning attack were ruthlessly exposed as Jets scored 43 runs in the first two overs of their innings, Arron Lilley conceding 23 runs off his first six deliveries and Kyle Jarvis leaking 20 off his over.
Mark Stoneman fell for ten runs in the third over but Mustard was on course to equal his county's fastest short-form fifty, which was achieved off 19 balls by John Hastings against Northamptonshire in 2014, when he skied George Edwards to Guptill at square leg.
By then, though, Durham Jets were 73 for two in six overs and the later loss of Clark and Ryan Pringle's wickets never looked likely to affect the outcome of what was a predominantly one-sided encounter.
Wagner and Edwards collected a couple of wickets apiece for Lancashire, who have now lost both their T20 games this season. Michael Richardson completed the victory and finished on 34 not out.