Surrey 154 for 4 (Sibley 40, Roy 36) beat Sussex 153 for 6 (Cachopa 45, Nash 39) by six wickets
Surrey kept their hopes of reaching the last eight of the NatWest T20 Blast alive with a comfortable six-wicket win over Sussex Sharks in front of a 22,601 crowd at The Kia Oval.
Having restricted Sussex to 153 for 6 on a slow pitch, Surrey paced their response perfectly and won the game with ten balls to spare when Chris Morris swung Mustafizur Rahman over midwicket for six.
It was Surrey's sixth win in the ultra-competitive South Group and they join Sussex on 12 points, but the Sharks only have one game left - at home to second-placed Glamorgan next Wednesday - and their chances of making the quarter-finals appear remote.
Surrey had been given a strong start by England opener Jason Roy, who made 36 off 25 balls, hitting six fours and a six.
Roy looked in the mood but was becalmed by slow left-armer Danny Briggs who came on in the powerplay and bowled Roy in his second over as the batsman slogged across the line. A clearly frustrated Roy angrily swished his bat at the stumps as he departed, an act which may earn him a rebuke from umpires David Millns and Alex Wharf.
Roy's opening partner Aaron Finch had gone in the third over, caught at backward point off a huge top-edge to give Jofra Archer, the Barbados-born fast bowler playing only his third game in the competition, the first of two wickets.
But Dominic Sibley and Rory Burns were determined not to squander Surrey's good start. The third-wicket pair added 42 in 27 balls and although Burns (13) was superbly caught at long leg by the diving Rahman, Sibley made a composed 40 off 31 deliveries with three sixes and a four to put his side in control.
He was athletically caught by Sussex captain Luke Wright at extra cover in the 15th over, but Surrey required just 38 runs at that stage and Morris (20) and Ben Foakes (22) eased them to their sixth win of the group stage.
Sussex, who had been put in, were 15-20 runs short in the end. With four overs to go they were 135 for 3 but Jade Dernbach and Tom Curran bowled superbly at the death, taking three wickets as Sussex cobbled together just 18 more runs.
Craig Cachopa and Matt Machan had put on 51 in 31 balls for the fourth wicket but they fell off successive Dernbach deliveries in the 19th over. Machan (18) top-edged a pull and Cachopa was held at long on for 45 (34 balls, 7 fours) while Chris Jordan gave Curran a deserved wicket when he holed out to deep mid-wicket in the final over.
Sussex were without fast bowler Tymal Mills because of ankle trouble and their leading scorer in this season's Blast Ross Taylor, who has joined up with New Zealand for their tour of South Africa.
In Taylor's absence they needed experienced openers Chris Nash and Wright to perform and although Nash played well for his 39 from 34 balls, Sussex captain Wright was out for just 7.
Surrey's seamers showed good control with Dernbach taking 2 for 25, Morris 2 for 21 and Tom Curran 1 for 20.