Cardiff Blues (11) 14 Try: Halfpenny Pens: Parks 3 Castres (3) 9 Pens: Bai 2, Bernard
Wales wing Leigh Halfpenny powers over to score his third try of the season
Wales international Leigh Halfpenny continued his impressive comeback from ankle injury with a try-scoring display to beat Castes in the Heineken Cup.
The wing scored in his first start for three months against Aironi last week and followed it up against the Castres with a man-of-the-match performance.
Halfpenny enhanced his Six Nations bid with Wales while Blues team-mate fly-half Dan Parks kicked three penalties.
Seremaia Bai replied with two penalties before Pierre Bernard's late kick.
But the Pool One victory, the Blues' first in four games in Europe, was academic as Dai Young's men have no chance of qualifying for the quarter-final.
The Blues, however, did keep alive their slim hopes of qualifying for the Amlin Challenge Cup, a tournament they won last season.
But they may be left to rue the losing bonus point the French visitors picked up to keep themselves in second place by a single point with one round of games to go.
Young's team, outplayed up front in Castres, dominated their scrum while skipper Paul Tito controlled the line-out, but they were unable to convert possession into points.
Castres, needing at least a victory to prevent Northampton winning the group, stole a Blues throw at the first line-out and laid siege to the home 22.
But had to settle for a penalty by centre Bai, who went on to miss a further shot at goal.
The Blues gradually came into the game and Dan Parks kicked two penalties to put them 6-3 up.
Both kickers missed further chances in a war of attrition, but the Blues then produced a rare moment of class for the game's only try.
Having turned the ball over in midfield, the home side spread it right, a looped pass from Parks followed by a neat kick ahead by Kiwi centre Casey Laulala.
Flying Wales winger Halfpenny reached it first, dribbling past a stranded French defender before picking up and setting off on a curving run around the covering tacklers and stretching over the line for his second try in successive games.
Scotland international Parks, however, missed the simple conversion.
The second half saw Castres again fall foul of referee Andrew Small, who responded to their persistent offending by showing a yellow card to replacement Wing Yoan Audrin, while Parks claimed the three points.
A Bai penalty kept the visitors, despite being down to 14 men, in the game but the Fijian, who began his European career in Wales with Cross Keys, missed a further kick from wide out after the returning Audrin had intercepted an errant pass by Blues hooker Rhys Thomas.
The home side were showing the greater adventure, with Laulala and Halfpenny always a threat but, after Tito had been held up short, Parks made a hash of a straight-forward drop-goal.
Replacement Pierre Bernard then kicked a long-range penalty to secure the vital bonus point and further diminish the possibility of the Blues going further in Europe this season.
Cardiff Blues: Czekaj, Halfpenny, Laulala, Roberts, Mustoe, Parks, Slater, Yapp, Thomas, Filise, Jones, Tito, Pretorius, M. Williams, Molitika. Replacements: G. Williams for Thomas (66), B. Davies for Jones (57), White for M. Williams (74). Not Used: Andrews, Hobbs, Sweeney, Hewitt, James.
Castres: Denos, Nicolas, Cabannes, Bai, Andreu, McIntyre, Albouy, Forestier, Bonello, Saayman, Rolland, Kulemin, Adamou, Malonga, Bornman. Replacements: Teulet for Denos (64), Audrin for Andreu (25), Bernard for McIntyre (74), Peikrishvili for Forestier (55), Giorgadze for Bonello (60), Ducalcon for Saayman (52), Tekori for Kulemin (45), Masoe for Adamou (60).
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