Battling Bristol recorded their first Aviva Premiership win of the season after sinking fellow strugglers Worcester 28-20 despite having centre Tusi Pisi sent off.

Samoa international Pisi was dismissed for a dangerous tackle after just 13 minutes, but Bristol were not to be denied in the quest for an opening Premiership victory this season at the 11th attempt.

An Ashton Gate crowd of 16,500 roared its approval as wing Tom Varndell's try hat-trick and 13 points from the boot of full-back Jason Woodward gave the Premiership's bottom club a lifeline.

Varndell's heroics - he also claimed a hat-trick against European Challenge Cup opponents Pau just before Christmas - gave him 89 Premiership career tries, leaving him just one short of equalling Mark Cueto's record.

Bristol closed the gap on 11th-placed Worcester to two points, with the Warriors proving unable to capitalise on their one-man advantage for more than an hour, despite lock Darren Barry and wing Dean Hammond scoring tries, plus a penalty apiece from Jamie Shillcock and Chris Pennell, with Pennell also landing two conversions.

Shillcock did not return to the action following Pisi's challenge, and Worcester missed his influence as Bristol dug deep, giving their supporters hope that Premiership survival can be achieved following a first top-flight league win since they beat the Warriors in March 2009 and then dropped into the Championship two months later.

Pisi was shown red after taking out Shillock in the air (Getty)

Pisi returned for Bristol after an 11-week injury absence, while acting head coach Mark Tainton made three other changes following last weekend's victory over Pau as he called up former Ulster lock Dan Tuohy for his Premiership debut, plus back-row pair Olly Robinson and Nick Fenton-Wells.

Worcester showed five changes as Hammond, Ben Te'o, Michael Dowsett, Na'ama Leleimalefaga and Christian Scotland-Williamson all featured, with Dewald Potgieter captaining the Warriors for only a second time in his career at Sixways.

Andy Robinson - in a role of television pundit after his stint as Bristol rugby director ended last month - was among a bumper Boxing Day crowd, with his former charges making a flying start by scoring 10 points in 10 minutes.

Woodward and Shillcock exchanged penalties, before Bristol cut open the Warriors defence when fly-half Billy Searle made a classy break and sent a jubilant Varndell over.

Bristol's joy at such a bright opening proved short-lived, though, when Pisi was ruled to have tackled an airborne Shillcock dangerously, sending the Worcester player flying and resulting in a red card from referee Wayne Barnes after he consulted television replays.

Shillcock departed for a head injury assessment, before Pennell cut the deficit with a short-range penalty and a period of sustained Worcester pressure reaped its reward when Barry crashed over from close range and Pennell's conversion gave the Warriors a 13-10 advantage after 21 minutes.

But Bristol were in no mood to play second fiddle, and Varndell pounced for his second try with a superb finish after being set free by scrum-half Will Cliff, and a gripping encounter saw the home side back in front.

Worcester have lost each of their last five in the Premiership (Getty)

Worcester were then reduced to 14 men - albeit temporarily - when Barry was sin-binned for collapsing a maul, and another Woodward penalty sent Bristol five points clear at the break after responding brilliantly to Pisi's early departure.

A scrappy third quarter ended with Woodward booting another penalty, but Worcester then conjured a superb breakaway try by Hammond that Pennell converted, only for Varrndell to complete his hat-trick just two minutes later, and another Woodward conversion restored an eight-point advantage.

It was a magnificent effort by Bristol, and they will head to Sale Sharks on New Year's Day with renewed confidence that they can achieve what has seemed mission improbable so far this season and avoid relegation.