Essex 320 for 5 (Pettini 126, Westley 108) beat Warwickshire 168 (Trott 51) by 152 runs
Essex's dominance of the visiting attack resulted in a total of 320 for 5, which proved well beyond Warwickshire's capabilitie as they were bowled out for 168 in 40.2 overs.
It proved an unhappy return for the former Essex batsman, Varun Chopra. He was soon regretting his decision to insert the home side as Pettini and Westley launched the Essex innings with an opening stand of 191 in 34 overs. He then suffered the ignominy of being out first ball when Warwickshire began their reply.
The Essex openers never looked in the slightest trouble as they treated pace and spin with equal comfort, producing a succession of drives, pulls and square cuts to progress at nearly a run a ball.
Respite only came when Westley was trapped lbw to offspinner Jeetan Patel but not before he had amassed 108, his second List A century with the help of a dozen fours and a six.
Pettini has been overlooked at Championship level, the form of Nick Browne relegating him to the sidelines. But in the one-day format, he is considered a vital component of their batting line-up in addition to his fine fielding. And he was to confirm his pedigree with a forceful 126 from 127 balls before he swung Oliver Hannon-Dalby to deep midwicket and was fourth out in the 48th over after striking 10 fours and two sixes.
Before Pettini's demise, Ravi Bopara also struck two sixes in making 39 from 33 balls before he dragged on against Chris Woakes.
The Essex innings finished on a high when Ryan ten Doeschate struck the final delivery over long-on for six to finish unbeaten on 21 from 12 balls.
Faced with such a daunting task, Warwickshire desperately needed to start their reply on a firm foundation but their hopes of doing so were soon shattered.
Chopra was caught and bowled by Topley, an inside edge finding its way into the bowler's hands via the batsman's pad. The tall left-arm paceman soon claimed another wicket, that of Will Porterfield, when the opener holed out to deep square leg.
Only 37 runs were on the board when Tim Ambrose became the third wicket to fall as he clipped Graham Napier to third man where David Masters pocketed a catch in the 13th over.
By the halfway stage, Warwickshire had limped to 92 for 5, by which time Rikki Clarke and Laurie Evans had been despatched to the pavilion leaving Jonathan Trott to salvage a little bit of pride for his team.
By then, however, he was fully aware that victory was out of the question for last season's beaten finalists but he did make something of a fight of it.
He reached his half-century by pulling Bopara for six but was out immediately afterwards for 51, made from 79 balls, when Kishen Velani took the third of his four catches at deep square leg to give off-spinner Westley another wicket and leave Warwickshire on 101 for 6. The same combination had earlier got rid of Clarke.
Although the tail wagged, putting on a further 67 runs in 13 overs, Essex were able to celebrate a comfortable victory and gain consolation for the misery Warwickshire inflicted upon them last season when they triumphed at Chelmsford in both the Royal London Cup and Twenty20 Blast at the quarter-final stage.