Indeed, Munster's Heineken Cup history with Castres extends to 10 games and in the words of former captain and current forwards coach Anthony Foley, those encounters were particularly 'feisty affairs.'
Reacting to today's draw, Foley said: "We're up against sides we know well. Northampton Saints, beaten finalists this year, we had them in our pool last season and then again in the quarter-final. The final scoreline (33-19) that day didn't reflect the closeness of the game.
"Then the Scarlets, we play them twice a season in the league and they are never an easy touch. They've a good European pedigree and of course Castres have been around a long time."
Foley feels that how the fixtures fall and how players come out of the Rugby World Cup later this year will have an influence on Munster's campaign.
"Yeah, the competition kicks off shortly after the World Cup final and how lads come through that will obviously have a bearing.
"Like when we played Northampton in the first round last season, Paul (O'Connell) and Jerry (Flannery) were just in their second game back and that was significant I think.
"So there's loads of factors to be considered not least that we've landed ourselves in a very interesting pool that will likely only provide one qualifier."