Bath surrendered an unbeaten home record stretching back more than a year as Cardiff deservedly took the spoils in a rain-drenched EDF Energy Cup clash at the Rec on Friday night, recording a fine if empty 14-6 away win.
There was little chance of either side progressing to the knockout stages of the EDF Energy Cup but the visitors looked by far the livelier outfit.
The conditions had an undoubted effect on the tactics and for 75 minutes the teams were separated only by the odd penalty.
However, Cardiff did manage to conjure a moment of magic, fashioning a brilliant length-of-the-field try begun by young full-back Jamie Roberts and finished off by flanker Robin Sowden-Taylor.
Cardiff's task, against a Bath side currently second in the Guinness Premiership, had been made all the harder by having 11 players on the injured list and giving up Tom Shanklin and Martyn Williams to the Barbarians.
The home side made seven changes, giving a first game of the season to Joe Maddock on the right wing, the New Zealander having been absent with hamstring trouble since the summer.
From the first minute Cardiff made light of the sodden conditions, monopolising possession until the spell was broken by a typically audacious counter-attack by Bath full-back Nick Abendanon.
When Bath did manage to wrest control of the ball from the hard-working Blues pack, scrum-half Michael Claassens was usually content to hoist kicks into the teeming rain.
Bath did attempt to ease the pressure by running out from their own line but Olly Barkley failed to spot Maddock on his left, was caught in possession and conceded a penalty. Cardiff fly-half Dai Flanagan goaled from 40 metres to open the scoring.
Bath roused themselves finally and thought they had scored when Maddock pounced on a cleverly-disguised kick to the corner by Butch James but the television match official ruled a knock-on. Barkley levelled the scores on 23 minutes however after Cardiff gave away one too many penalties.
Scrum-half Jason Spice fell foul of the TMO at the other end when he needlessly lost control of the ball after doing all the hard work in finding a gap around a maul on the half-hour.
It was left to Flanagan and Barkley to swap penalties just before the break as the teams went in search of some dry jerseys.
Barkley was wide with a long-range penalty soon after the interval after Gareth Thomas was flagged for a high tackle but that was the only scoring opportunity of note in the third quarter.
Just after the hour, Cardiff's territorial dominance was rewarded when Spice broke clear only for a supporting player to be held back by Bath lock Peter Short.
He was sent to the bin and Flanagan kicked his third penalty to ease the visitors into a 9-6 lead on 64 minutes. Although down to 14 men Bath had perhaps their best spell of the game until hit with Sowden-Taylor's sucker-punch just before time.
Pens: Barkley 2
For Cardiff Blues:
Pens: Flanagan 3
Bath: 15 Nick Abendanon, 14 Joe Maddock, 13 Tom Cheeseman, 12 Olly Barkley, 11 Michael Stephenson, 10 Butch James, 9 Michael Claassens, 8 Daniel Browne, 7 Michael Lipman, 6 Jonny Fa'amatuainu, 5 Peter Short, 4 Steve Borthwick, 3 Lorne Ward, 2 Pieter Dixon, 1 Matt Stevens/Laurence Ovens.
Replacement: 16 Lee Mears, 17 Paulica Ion, 18 James Scaysbrook, 19 Martin Purdy, 20 Chris Goodman, 21 Nick Walshe, 22 Shaun Berne.
Cardiff Blues: 15 Jamie Roberts, 14 Tal Selley, 13 Gareth Thomas, 12 Dafydd Hewitt, 11 Tom James, 10 Dai Flanagan, 9 Jason Spice, 8 Xavier Rush (c), 7 Robin Sowden Taylor, 6 Ma'ama Molitika, 5 Paul Tito, 4 Deiniol Jones, 3 Gary Powell, 2 T Rhys Thomas, 1 John Yapp.
Replacements: 16 Gethin Jenkins/Taufa'ao Filise, 17 Gareth Williams, 18 Scott Morgan, 19 Andy Powell, 20 Ben White, 21 Darren Allinson, 22 Ryan Howells.
Referee: Nigel Owens (Wales)
Touch judges: Huw David (Wales), Wayne Davies (Wales)
Television match official: Matt Peters (England), Graham Hughes (England)