Kent Spitfires suffered a 22-run defeat to Hampshire on Thursday night despite a superb unbeaten 89 from skipper Rob Key.
It was a first reverse in this year's competition for Key's side as the hosts produced a strong finish with the bat to post 171-7 before some fine bowling kept Kent at arm's length throughout much of the chase.
Former Kent man Michael Carberry was their tormentor-in-chief once again as he amassed 73 from 58 balls with eight fours and two sixes before having his stumps spattered by Doug Bollinger in the penultimate over.
The Aussie paceman was the pick of the Kent bowling attack - which included two spinners in the form of Adam Riley and the returning James Tredwell - as he claimed 3-19.
Jimmy Adams made 47 from 26 balls and put on 66 for the second wicket with Carberry before being trapped lbw by Riley while Tredwell responded to being slapped for six by Glenn Maxwell by having him caught in the deep by Darren Stevens the next ball.
A fine runout by Stevens saw Adam Wheater depart fur a duck but the hosts added 18 from the final eight deliveries to pass 170, with both Stevens and Mitch Claydon going for 44 apiece from their four overs.
The reply began slowly and and asking rate of more than eight an over soon rose to double figures as Key and Daniel Bell-Drummond struggled to get the ball away.
Rob Key in action against Gloucestershire Picture: Barry Goodwin
After putting on 31 in the first 31 deliveries Bell-Drummond miscued the first ball from spinner Danny Briggs to James Vince for 12 and Sam Northeast then joined Key to put on 89 in little over 10 overs for the second wicket to keep the visitors in the game.
He eventually departed when he clipped a ball from spinner Will Smith to Owais Shah after making 35 from 27 deliveries.
Stevens came in with the game on the line but was dropped off the first ball by Sean Ervine before being bowled by Briggs moments later for one.
With 47 needed and less than four overs remaining, Sam Billings came in but he too departed swiftly (2) to leave Key and Alex Blake (7 not out) with an uphill struggle.
Key struck three big sixes and six fours, but was unable to steer his side any closer, as stifling bowling at the death meant that the 42 required from the final three overs became 37 from two and 32 from the final over.
As it was the 2010 and 2012 winners and 2013 semi-finalists strengthened their grip at the top of South Group while second-placed Kent will seek to return to winning ways when they host struggling Middlesex Panthers at Canterbury on Friday (7pm).