|T20 Blast; County Ground, Hove|
|Glamorgan 164-7 (20.0 overs)|
|Sussex 165-2 (14.5 overs)|
|Sussex won by eight wickets|
Luke Wright scored a superb unbeaten 92 to steer Sussex to an eight wicket win over Glamorgan with 31 balls to spare.
Wright and Chris Nash (50) put together a century stand - just as they did when Glamorgan were beaten by 10 wickets in Cardiff in June.
Ben Wright's career-best 63 off 46 balls was the spine of the Glamorgan innings but no one else passed 20 runs.
The Welsh county will have to win their final two games in the competition to have a chance of making the last eight.
Sussex are looking good however, lying second in the South Group with two matches left to play.
Glamorgan's batsmen struggled from the start, and their total of 164-7 looked to be around 30 runs short of par.
Sussex openers Luke Wright and Nash were quickly into their stride taking full advantage of the early fielding restrictions to find the gaps and the boundaries.
They added 64 runs in the power-play, while 100 came up in the 10th over with Glamorgan's bowling changes unable to stop the flow of runs.
When Nash skied Graham Wagg to David Lloyd in the deep with the total on 117 he was the first Sharks player to be dismissed by Glamorgan in two T20 matches this season.
And Wagg also had Matt Machan caught close to the boundary as Donald took a fine tumbling catch.
But a volley of sixes from Wright and George Bailey ended the game in the 15th over to delight the packed home crowd.
Glamorgan top-scorer Ben Wright failed to take the field in the Sussex innings after being hit on the helmet while batting.
Leaders Kent are Glamorgan's next opponents at Tunbridge Wells and the round off their campaign at home to Gloucestershire.
Glamorgan captain Jacques Rudloph told BBC Wales Sport: "I thought the way Luke Wright and Chris Nash played in the first five overs blew us out of the window, it's really disappointing for us.
"We've got a tough four days coming up against Essex in the Championship at Chelmsford, but hopefully when we play Kent at Tunbridge Wells, we can have a good game."