Hampshire missed the chance to move three points clear at the top of Group B of the Clydesdale Bank 40 after going down to a 50-run defeat to Somerset.
A fine knock of 95 from opener James Vince couldn't prevent the Royals falling well short in their pursuit of a target of 229 at the Ageas Bowl.
Liam Dawson (36) and Michael Bates (16) were the only other home batsmen to reach double figures, the former helping put on a 73-run stand for the fifth wicket after the innings had slumped to 49-4.
Vince was the final wicket to fall after being left to do it all on his own, trapped lbw by Gemaal Hussain having hit eight fours and a six in his 87-ball knock.
Hampshire finished up on 178 all out, paceman Steve Kirby the pick of the Somerset attack with impressive figures of 3-19 from six overs.
There was also two wickets for Peter Trego, his double strike completing a fine all-round match from the 31-year-old after he had earlier smashed 61 from just 31 deliveries at the top of the order.
Trego's early onslaught made up for the loss of Marcus Trescothick for just two, the former Kent player dominating a second-wicket alliance of 73 with Chris Jones (23) before slapping spinner Dan Briggs (2-39) to point.
Jos Buttler weighed in with an entertaining 51 but when he became Briggs' second victim, toe-ending an attempted reverse sweep to cover, Somerset looked in danger of subsiding at 180-6.
But Alex Barrow held things together with an unbeaten 29 before Hussain provided some late fireworks, hitting two huge sixes to help take 23 runs from the final over and carry his team's score to 228-8.