The penny really should have dropped with the players of London Irish last night, especially as Sam Warburton, famously sent off during last month's World Cup semi-final between Wales and France for driving a rival beyond the horizontal in a tackle and landing him smack on his back, was there on the field to serve as a reminder.
So what did Steve Shingler, the young Exiles centre, do midway through the first half? Why, he drove his opposite number Dafydd Hewitt beyond the horizontal and landed him smack on his back. The result? You guessed it.
Shingler knew he would be shown a red card, just as the Wales captain received one in Auckland, and off he trudged, leaving his colleagues, already off their game and under the hammer, in a heap of trouble.
Barely able to cope with Lloyd Williams' razor-sharp work at scrum-half and Casey Laulala's off-loading game in midfield during the 19 minutes they spent with a full complement of personnel, the visitors were hardly likely to keep their tormentors quiet after going a man down.
Yet strange to relate, the accurate Tom Homer kept London Irish in the contest by banging over penalties from a variety of angles and ranges. Even after Williams took advantage of some excellent restart work from Michael Paterson to zip away from Nick Kennedy on an arcing run to the line and reduce the Premiership club's chances of avoiding a second successive European defeat to something resembling zero, they hung in there by hook or by crook.
Denied the services of two injured international backs in Leigh Halfpenny and Jamie Roberts, the Blues still sought to play with ball in hand and showed no little adventure in ensuring that their powerful wings, Alex Cuthbert and Tom James, were fully involved early on. For all that, their opening try was down to a couple of tight forwards: the lock Paul Tito, who took a clean catch at a close-range line-out, and the hooker Rhys Thomas, who burrowed over from the ensuing maul.
With Dan Parks landing the majority of his early kicks, it looked for all the world as though the Blues would be out of sight by the interval, especially as the Exiles, usually so reliable in contact, were coughing up ball for a pastime. At one point, the diminutive Williams stripped the ball clean away from David Paice, a hardened front-row forward. The look of embarrassment on Paice's face told the tale.
Yet the Blues' technical indiscipline allowed Homer enough shots to keep his side interested – the visitors were also helped by the Blues management's peculiar decision to withdraw both Williams and Casey Laulala before the end of the third quarter – and it was not until Parks kicked a fourth penalty from the left of the sticks with 11 minutes left that the outcome was confirmed.
Even then, Homer had a late say, securing a losing bonus point with a sixth successful kick.
Cardiff Blues: C Czekaj; A Cuthbert, C Laulala (G Evans 59), D Hewitt, T James; D Parks, L Williams (R Rees 59); G Jenkins, R Thomas (M Breeze 71), T Filise (S Andrews 60), B Davies, P Tito (capt), M Paterson, S Warburton, X Rush (M Molitika 21).
London Irish: T Homer; T Ojo, J Ansbro, S Shingler, A Thompstone; D Bowden, R Samson (P Hodgson 60); C Dermody (capt, A Corbisiero 56), D Paice (J Buckland 53), F Rautenbach (P Ion h-t), N Kennedy, M Garvey (J Sandford 61), D Danaher, R Thorpe (J Gibson 53), J Sinclair.
Referee: J Garces (France).