Sussex missed the chance to qualify for the semi-finals of the Clydesdale Bank 40 at the PROBIZ County Ground where the Group A leaders lost to Kent by 14 runs.
A win would have taken the Sharks through to the last four, but now they will have to avoid defeat to Middlesex at Lord’s on Monday to make sure.
They were cruising towards a target of 217 at 76 without loss after 10 overs until they suffered a collapse of four wickets for seven runs in three overs.
Just before the slide, Darren Stevens had both openers, Ed Joyce and Chris Nash, dropped by Martin van Jaarsveld off successive deliveries.
They failed to make the most of their reprieves. Joyce, who had dominated the opening stand with a 34-ball 49, was caught behind off Stevens and in the next over van Jaarsveld, anxious to atone, ran out Lou Vincent.
Stevens then had Nash lbw with one that nipped back and Sussex were 83 for four when Murray Goodwin sliced Adam Ball to the finer of the two backward points.
Michael Yardy and Joe Gatting again turned the game towards the Sharks with a fifth-wicket stand of 50 in nine overs. But Gatting was run out by James Tredwell for 34, Ben Brown was caught behind and Michael Yardy walked down the wicket and was stumped for 23.
Against tight Kent fielding, and some clever off-spin from Adam Riley, it was too much for the lower order, even though Wayne Parnell hit an impressive 40.
After Kent chose to bat on a pitch with some nip and bounce, Chris Liddle broke through in the second over when he pushed one across Joe Denly to have him caught behind.
Daniel Bell-Drummond, opening in place of the injured Rob Key, produced some eye-catching cover-drives in his 28-delivery 30, but he was too close to the ball when he cut Liddle to Gatting in the covers.
The best Kent innings came from in-form Azhar Mahmood, whose 58 from 53 balls included eight fours and a six.
He was out when he tried to hit Monty Panesar to leg and got a leading edge, but Kent were reasonably satisfied at 120 for three at the halfway stage of their innings.
However, their remaining key players failed to fire. Stevens was lbw to a quicker delivery from Yardy and van Jaarsveld was caught at long-off for 31 when he tried to push up the scoring rate.
It was the first of six wickets to fall for 65 runs, as Panesar and Parnell each finished with three.
Kent, all out for 216 to the last ball of he 40th over, were underdogs at that stage but fought back with the ball.