Cardiff Blues recovered from an early onslaught to claim an entertaining 35-26 victory over the Scarlets at Arms Park on Friday.
The Blues' success moves them into second place in the competition after what was a seesaw eight-try thriller, which kept the 10,216 Arms Park crowd warm on a chilly night.
A seventeen-point contribution from Kiwi full-back Ben Blair helped see the Blues home and, if Leinster look to have the title wrapped up, Dai Young's side struck a major blow in the battle to be the top Welsh region.
The Blues, attempting to shrug off last week's Heineken Cup disappointment, showed early willingness to give the ball some air, but were hit by a two-try blitz before the first five minutes had elapsed.
Acting captain Dwayne Peel, in his 50th league match, finished off a move he began and a break by full-back Ceiron Thomas was rounded off by young centre Jon Davies.
Two conversions by Stephen Jones left the Blues stunned and they suffered again in a bad 60 seconds for the Robinson brothers.
A burst by centre Jamie ended with another addition to his long list of injuries, before brother Nicky fumbled a loose ball with the line at his mercy.
Australian centre Marc Stcherbina was the next to knock-on in the Scarlets' 22, but the visitors lost Alix Popham, who was yellow carded for an offence at the resulting scrum, and Blair's penalty put the home side on the board.
Fly-half Robinson then made up for his earlier error, crossing after good work by the evergreen Gareth Thomas. But replacement centre Tom Shanklin and Thomas were both held up over the line as the Blues piled on the pressure.
And they were finally rewarded when scrum-half Jason Spice sent wing Tom James over for his eighth try of the season, with Blair's kick giving the Blues an unexpected interval lead.
James was the Blues' hero again after the break when he set off on a 50-yard gallop through the Scarlets defence and put the supporting Stcherbina under the posts - Blair adding the extras.
The departure of Spice to the sin-bin then offered the Scarlets an opportunity to hit back and they grabbed it, a superb run by replacement full-back Morgan Stoddart preceded Wales' Grand Slam winger Mark Jones flying over.
Within two minutes, the Scarlets were back in the lead, with a bonus point to boot, as Stoddart rounded off a length-of-the-field move which Stephen Jones converted.
Spice never returned from his time out, being replaced by Richie Rees, who immediately made a sniping run which almost reached the whitewash before Mark Jones became the third player carded for preventing an early release - Blair's penalty putting the Blues back in front.
And when Blues' all-action flanker Maama Molitika stole a Ken Owens line-out, which resulted in Blair crossing on the opposite touchline, the Blues also claimed a bonus point.
Nicky Robinson smartly taken drop-goal completed the scoring, rounding off a fine performance in his first start since December, and robbing the visitors of a losing bonus point in a pulsating clash.
For Cardiff Blues:
Tries: Robinson, James, Stcherbina, Blair
Con: Blair 3
Tries: Peel, Davies, M Jones, Stoddard
Con: S Jones 3
Yellow card: Alix Popham (Scarlets - 22 mins), Jason Spice (Blues - 51 mins), Mark Jones (Scarlets - 64 mins).
Cardiff Blues: 15 Ben Blair, 14 Gareth Thomas, 13 Jamie Robinson, 12 Marc Stcherbina, 11 Tom James, 10 Nick Robinson, 9 Jason Spice, 8 Mark Lewis, 7 Martyn Williams, 6 Mamma Molitika, 5 Scott Morgan, 4 Deiniol Jones, 3 Gary Powell, 2 T Rhys Thomas, 1 John Yapp.
Replacements: 16 Taufa'o Filise, 17 Gareth Williams, 18 Paul Tito, 19 Xavier Rush, 20 Richie Rees, 21 Dai Flannigan, 22 Tom Shanklin.
Scarlets: 15 Ceiron Thomas, 14 Dafydd James, 13 Regan King, 12 Jonathan Davies, 11 Mark Jones, 10 Stephen Jones, 9 Dwayne Peel (c), 8 Alix Popham, 7 Gavin Thomas, 6 Dafydd Jones, 5 Scott MacLeod, 4 Vernon Cooper, 3 Bruce Douglas, 2 Matthew Rees, 1 Iestyn Thomas.
Replacements: 16 Phil John, 17 Mahonri Schwalger, 18 Nathan Thomas, 19 Simon Easterby, 20 Gavin Cattle, 21 Rhys Priestland, 22 Morgan Stoddart.
Referee: Nigel Owens