Somerset's NatWest Pro40 title bid will go to the final day of the season after they thrashed Worcestershire by 84 runs at New Road.

The second-placed Sabres must now beat Durham at Taunton a week on Sunday and hope leaders Sussex fail to defeat Worcester the same afternoon to clinch their first one-day league crown since 1979.

Last night's game was a title eliminator and the Royals were effectively knocked out by 109 from their former batsman Zander de Bruyn.

De Bruyn played one season for Worcestershire in 2005 with mixed success, except when he made 161 against Somerset in a Championship game.

He recently signed a new two-year contract in Taunton and will be a contender to be vice-captain when Marcus Trescothick replaces Justin Langer as skipper next year.

The South African injured his groin halfway through his innings and was unable to bowl or field when Worcester tried to chase 237.

But he was not needed as Alfonso Thomas bowled the hosts' openers in his first four overs.

First Stephen Davies (8) chopped on attempting a hook before Vikram Solanki (5) was unsettled by a bouncer and played across the next ball, which was angled into him to lose his middle stump.

After that Worcester were always going to struggle under the floodlights and Moeen Ali failed to pick Ben Phillips' slower ball and nicked on to his stumps for nine.

Phillips then got one to seam away from Ben Smith and take his off stump for one to make it 51-4.

It was 75-5 when Daryl Mitchell became the fifth Worcester batsman to be bowled after he missed a Pete Trego yorker for 15.

Trego then trapped Stephen Moore leg before wicket for 49 and former Somerset seamer Gareth Andrew whacked 27 before he was also bowled, this time by one that turned into him from Arul Suppiah.

Worcester were eventually hustled out for 152 in 36.1 overs.

Earlier, de Bruyn's run-a-ball innings – his first hundred in any cricket this season and his maiden one-day ton in the county game – had formed the centre-piece of Somerset's imposing 236-5.

The fit-again Langer made 45 runs from 62 balls and waited until his 57th to hit his first four.

At the start of the game, Yeovil-born seamer Andrew had rocked his old club's top order with the first three wickets.

First Craig Kieswetter got an edge before James Hildreth played on for a duck. Trescothick's 30 from 31 balls ended when he hooked Andrew down deep backward square leg's throat.

Somerset begin their final Championship game against Worcestershire at Taunton tomorrow.