The strength and class of Colin Ingram overcame a challenging pitch at The 1st Central County Ground to give Glamorgan their second win in the Metro Bank One Day Cup.
Ingram, returning to the side, hit 73 off 75 deliveries, with eight fours and a six over mid-on, as Glamorgan chased down 276 to win with 21 balls remaining. But it might have been a different story if the powerful left-hander had not been dropped by Harrison Ward at point off Sean Hunt when he had made just three.
Glamorgan lost opener Tom Bevan in the second over, bowled by Fynn Hudson-Prentice for a duck. But then Ingram and Eddie Byrom (69) piled on 145 for the second wicket in 23 overs to put Glamorgan on top.
Glamorgan continued to lose wickets - with cameos coming from captain Kiran Carlson and Ben Kellaway - against a tight ring of Sussex fielders. But a typically cool-head innings by Sam Northeast, who made an unbeaten 40, saw his side home.
Both sides had gone into the match with one victory in four matches and needing to win all their remaining fixtures to have any realistic chance of progressing to the latter stages of the competition.
Sussex decided to strengthen their batting by bringing in Ward for his first game in the competition this season. Sussex had chosen to bat with the best of it coming in a stand of 113 in 15 overs between James Coles (59 off 56) and Hudson-Prentice (66 off 54).
Ward and Tom Haines made a slow start, with just 14 runs coming off the first five overs. But they accelerated with such purpose that they scored 50 off the first ten-over powerplay and looked set for a total of well over 300.
They lost momentum when the unfortunate Ward, who had struck a six and five fours in a 32-ball 35, was run out responding to a call for a quick single.
After that, the top order Sussex batsmen struggled on a slow pitch, which Glamorgan exploited by bowling 29 overs of spin, with Carlson and Kellaway impressive, though the slow left-armer Prem Sisodiya proved a little expensive.
Tom Alsop, cutting at a delivery that was too straight and full for the purpose, fell next, Haines was bowled by what appeared to be a slower delivery from Zain-ul-Hassan and Tom Clark, was caught off a leading edge.
Cheteshwar Pujara, who averaged of 89 in this competition last year, and who already has two centuries in the current campaign, typically scores steadily while others bat around him. But now, needing to be more aggressive, he stepped down the pitch and crashed the ball at Carlson who took a sharp caught and bowled.
At 142 for five in the 32nd over, 19 year old James Coles, who struck five fours, and Hudson-Prentice, who hit three fours and two sixes, pulled the innings round. But it never looked likely to be enough against a strong Glamorgan batting side.
Report provided by ECB Reporter's Network