An uncharacteristic, quite unfathomable performance, unquestionably the worst in two seasons, has jeopardised Connacht's chances of qualifying for the European Shield quarter-finals.
Neither the extremely difficult conditions nor the bizarre decisions of Italian referee Claudio Giacomel can be used as excuses: Connacht were beaten all over the park by a side riding high after victory in France against Racing Club.
Connacht coach Glenn Ross had every reason to expect that the two previous tough outings against Narbonne and Ulster would have provided the platform for Connacht to build on their European success.
But, he said: "It seems as if we have to play against the best to bring out the best in us. I'm not taking anything away from Caerphilly, they out-played us, but for some reason we struggle to come to terms with teams we should be able to beat."
From start to finish, Caerphilly out-played their opponents, gaining in confidence in front of an appreciative, if small, 800-strong home support. Their man of the match, full back Brett Davey, kick-started the onslaught with a penalty after three minutes. Then, when Connacht were a man short - as number eight Barry Gavin was forced off with a torn shoulder muscle - the home side took advantage. Referee Giacomel continued play and winger Sean Marshall swept into the left corner against a stretched defence.
There was no let-up. Welsh international centre Roger Bidgood got their second try after 17 minutes. Davey converted and added three more penalties before the break. Connacht's only answer was an Eric Elwood penalty after 20 minutes.
If Connacht failed to exploit a perfect scoring opportunity before the break, they lost two golden chances immediately afterwards through a lack of finishing.
Instead, Davey stretched the lead with a 47th-minute penalty, and when he went through for a try some five minutes later from inside his own half, it was goodnight for Connacht.
A score by Connacht's Nigel Carolan after 74 minutes was cold comfort for a side that now needs a comprehensive victory over Racing Club on Saturday.
