While Perpignan went all the way to the European final in Dublin after their Stradey Park success, the Scarlets were left licking their wounds and scratching their heads.
That night last April still haunts Davies, who knows that nothing less than back-to-back victories over Llanelli's Twin Town will suffice if they are to maintain their proud record of reaching the last eight.
The Welsh cup kings have yet to transfer their domestic dominance onto the continent but the assistant coach was crystal clear over where his team went wrong last term.
'When we played Perpignan I think we took a lot of things for granted and as a result we fell badly short of all the goals we had set ourselves,' said Davies.
'I think we all look back at that game and think about it and where we went wrong and I'm sure that if the players were honest with themselves they will say that they were complacent.
'You only get a couple of chances in Europe and you have to make sure you prepare for every opportunity properly, both physically and mentally, for what is going to be thrown at you.
'You can sometimes get away with things at home but not against the quality you face in Europe.
'We had worked hard to win our group and get home advantage in the quarter-final and we let ourselves down. It was painful then so I don't think there's any danger of it happening again this weekend. We have to make it doesn't. It's a vital home game that we have to win and we can't look any further than that.
'One of the values of this club is that it is down to earth but with big ambitions and we have always managed to keep expectations in hand.
'There has been a lot of honest talking this week as no one was happy with the game against the Ospreys last week. Obviously we were delighted with the result but the performance left a lot to be desired.
'The biggest area for concern was the set pieces where we just did not get going and so didn't give our backs the platform to build. We cannot afford to do that against a big, physical pack like Agen's.
'They have also got some big ball carriers behind the scrum like centre Conrad Stolz who played a lot of rugby in South Africa and their full-back Pepito Elhorga, who we will have to watch carefully.'
The Scarlets, however, have been boosted by Scott Quinnell's recovery from a shoulder injury after lasting less than half-an-hour against the Neath-Swansea Ospreys last week.
Quinnell further aggravated the problem in a training ground collision with Salesi Finau which, according to teammates, registered on the richter scale.
'It's an injury that he has been playing with for more than a year now and occassionally crops up. It's like having a dead arm and causes Scott quite a bit of pain and anxiety but it tends to go quite quickly.
'It's something we are aware of and it's just a question of managing his rehab and prehab.'
There was further good news with crocked wing Mark Jones, who has yet to play for the Scarlets since returning from the World Cup due to a knee problem, is among the replacements after coming through a run out in the Welsh Premiership at the weekend.
That gives Gareth Jenkins the luxury of naming the same side originally named against The Borders in their last European outing, though Adam Jones was a late replacement for the injured Chris Wyatt.
Llanelli Scarlets: B Davies; G Evans, M Taylor, M Watkins, S Finau; S Jones, D Peel; I Thomas, R McBryde, J Davies, V Cooper (capt), C Wyatt, D Jones, S Quinnell, S Easterby. Replacements: P John, A Gravelle, A Jones, D Hodges, M Phillips, G Bowen, M Jones.