Worcestershire flew past 200 in the 40th over, with Cullen’s late knock worth its weight in gold, accessing all areas of the ground with a flurry of inventive shots in a siege against a beleaguered bowling attack despite losing partner Kashif for an impressive 65.
The Academy graduate registered a maiden List A fifty from just 43 balls and showed no signs of slowing as he motored to a career-best 72, but had his wings clipped in the 46th over, with his side 260-6.
Cullen’s enterprising hand had produced five fours and four sixes, with the Rapids topped up by Tom Taylor (19) and Ben Allison (18) in the final embers of their innings to post a competitive 307-8.
In the scorching afternoon sun, it was the visitors who made the stronger start to the run-chase, with Ali Orr and Nick Gubbins adding 61 for the first wicket, keeping Tom Taylor and Matthew Waite at bay.
Worcestershire were made to wait until the 16th over for an opening, keeping the run-rate below five an over in the process, but the defending champions made sure to cash in on their opportunity.
Ben Allison and Harry Darley traded wickets exactly two overs apart in a crucial double blow that stunted Hampshire’s progress at 76-2.
The previously untroubled chase was thrown off course in style as first change seamer Allison (2-60) lured Orr into a loose shot through the off-side, which the left-hander could only chop back onto his own stumps to end his promising innings for 27.
From the other end, Darley (1-51) doubled the delight when he put an end to Fletcha Middleton’s scratchy stay at the crease for just three, as the Rapids surged into life.
Fresh off the back of career-best figures on Friday, off-spinner Fateh Singh was thrown the ball by skipper Libby in the 22nd over, with the pressure beginning to build on the away side who were needing upwards of eight an over before drinks.
Gubbins made his way to a typically stubborn half-century but could only add seven more to his total when the evergreen Tom Taylor returned with a bang to snare the skipper courtesy of a brilliant diving catch by Darley at extra-cover.
With their tails up, the Rapids turned the screw, showing shades of the cutting edge that took them to last year’s title as Matthew Waite curtailed Atoshock Sharma’s cameo for 11, picking up a vital fourth wicket.
Predictably, the Hampshire resistance arrived, with the hosts frustrated by a century stand between Australian Jake Lehman and Tom Prest that steered the game deep into the evening.
Typically, the hosts were far from done and turned the tide back in their favour with two wickets in the space of three balls that put the hosts back on course for victory.