Gloucester's decision to allow Willie Walker to play for Worcester backfired spectacularly as the on-loan fly-half kicked the Warriors to a shock 14-10 victory at Sixways on Sunday - and closer to Guinness Premiership safety.
Walker joined Worcester on loan last month after Gloucester recruited Carlos Spencer from Northampton. But there was no clause in the agreement which prevented Walker playing in this fixture and he proved a pivotal figure, landing three penalties in nine first-half minutes.
In contrast Spencer fluffed a kickable first minute penalty and he struggled to spark his three-quarters in a sloppy Gloucester performance which dented their hopes of a play-off place.
Gloucester dominated the game for long periods but they were frustrated by the ferocity and commitment of Worcester's defence, particularly in a scoreless second half, and had to settle for a first half penalty try to secure the losing bonus point.
To add insult to injury Worcester's only try was scored by former Gloucester winger Marcel Garvey, one of three ex-Cherry and Whites players in the Warriors side for this passionate local derby which attracted a record capacity crowd of 12,024 to Sixways.
Garvey's try came after Gloucester had dominated the first 15 minutes but failed to find a way through Worcester's defence - although it required a crunching tackle from Chris Latham to deny Luke Narraway.
Worcester's former Australia international full-back suffered a dislocated shoulder for his efforts which forced a reshuffle with Walker moving to full-back.
But Worcester gave Gloucester a lesson in finishing from their first attack of the game. Captain Pat Sanderson rumbled upfield and when the ball was moved right, Garvey's nimble footwork took him through a thicket of Gloucester forwards.
Gloucester responded with a ferocious forward effort that put Worcester's rookie tighthead prop Callum Black under pressure on his first start. When Worcester were penalised at three consecutive five metre scrums referee Dave Pearson lost patience and awarded Gloucester a penalty try which Spencer improved.
Worcester stabilised their scrum by replacing Black with former Wales prop Darren Morris and they went back in front when Walker capitalised on Gloucester's poor discipline.
Gloucester regained their some of their composure when Spencer trimmed the deficit to four points with a penalty on the stroke of half-time.
Gloucester began the second half as they had the first, pounding away at Worcester's defence but they could not find a way through.
Spencer almost sliced through but Matthew Watkins could not make it to the line. Spencer then knocked on as he tried to cross under the posts and Worcester scrum-half Ryan Powell denied Narraway with a last-ditch tackle that forced the England back-row forward to fumble.
Having absorbed the pressure Worcester finally broke out of defence with former Gloucester hooker Chris Fortey breaking from a ruck and Walker taking play deep into the visitors' 22 with a raking touch kick.
Walker was then short with a long range penalty attempt but Olly Barkley was also off target when he went for goal from close to half-way.
Gloucester had time for one last attack but centre Matthew Watkins fumbled as Worcester's eager defence pressed forward and the chance went begging.
For Worcester Warriors:
Pens: Walker 3
Worcester Warriors: 15 Chris Latham, 14 Marcel Garvey, 13 Rico Gear, 12 Dale Rasmussen, 11 Miles Benjamin, 10 Willie Walker, 9 Ryan Powell, 8 Kai Horstmann, 7 Pat Sanderson (c), 6 James Collins, 5 Will Bowley, 4 Greg Rawlinson, 3 Callum Black, 2 Chris Fortey, 1 Matt Mullan.
Replacements: 16 Darren Morris, 17 Aleki Lutui, 18 Graham Kitchener, 19 Netani Talei, 20 Jonny Arr, 21 Matthew Jones, 22 Alex Grove.
Gloucester: 15 Olly Morgan, 14 Iain Balshaw, 13 Matthew Watkins, 12 Anthony Allen, 11 James Simpson-Daniel, 10 Carlos Spencer, 9 Rory Lawson, 8 Luke Narraway, 7 Andy Hazell, 6 Apo Satala, 5 Alex Brown, 4 Will James, 3 Greg Somerville, 2 Olivier Azam (c), 1 Nick Wood.
Replacements: 16 Scott Lawson, 17 Jack Forster, 18 Adam Eustace, 19 Akapusi Qera, 20 Gareth Cooper, 21 Ryan Lamb, 22 Olly Barkley.
Referee: Dave Pearson