Chris Nash and Ed Joyce put on a fourth-wicket stand of 173 as Sussex eased to a 61-run Duckworth-Lewis win over Northamptonshire.
Both Nash and Joyce fell just short of centuries but their respective efforts of 95 and 90 helped Sussex to a total of 215-7 in the Yorkshire Bank 40 Group A contest.
Australia paceman Trent Copeland took career-best figures in one-day cricket of 5-32, but the rest of the hosts' attack was kept firmly under wraps by Sussex.
Northamptonshire's reply was interrupted by the weather but they were well short of a winning position on 122-9 when rain forced play to be abandoned.
Sussex won the toss and chose to bat, a decision which looked as if it would have dire consequences when they slumped to 12-3 in the sixth over.
But the fourth-wicket pair of Nash and Joyce recovered the Sharks' innings with Joyce reaching 50 off 61 balls and Nash following suit from 68 deliveries.
The duo continued to keep the scoreboard ticking over before the spectacular partnership was finally broken when Joyce pulled Steven Crook to Copeland at short fine leg.
Copeland accounted for Ben Brown (6) and Nash before completing his five-wicket haul when Chris Jordan (1) played on to his stumps in the final over.
Initially chasing 216, Northants were reduced to 78-4 within 20 overs before a 40-minute rain delay interrupted the action.
Chris Jordan (3-20) and Chris Liddle (3-31) continued to knock the wickets over before heavy rain finally put Northants out of their misery. Crook top-scored with 25.