And then there were four - Leinster, Northampton Saints, Newcastle Falcons and Stade Français Paris are the sole 100 per cent teams left at the halfway point of the Pool stage.
But Leinster coach Declan Kidney knows his Pool 2 table-toppers must conjure up a rare win in France when they take on Bourgoin on Friday night if they are to keep their quarter-final qualification momentum going.
Leinster have won just one of their eight visits to France - beating Montferrand (now Clermont Auvergne) 23-20 in the 2002 / 2003 tournament.
"I am happy with the way things have gone so far," said Kidney.
"But we are well aware that two of our matches have been at home and now we face successive away games against Bourgoin and Bath - and that is what makes this tournament so great, just how many teams can stay in contention right until Round 6.
"Our three wins won't count for anything if we don't win away from home - and Leinster have only once won in France. We are halfway through the Pool stage with three from three but that does not mean anything yet."
And while Bourgoin prop up Pool 2 as one of only two teams who have failed to pick up a solitary point so far, Kidney is wary of home pride when it comes to French clubs playing on their own patch.
"It will be completely different come Friday night," he said. "I know Bourgoin well from previous games against them and they are a very proud club who won't want to lose at home.
"I was at Bourgoin with Munster last season when we won a tight game 18-17 and I was also there in 1998 when they gave Munster a real hiding.
"Stade Pierre Rajon is a great European venue and home advantage is such a huge thing in the Heineken Cup."
Reggie Corrigan's team blasted Bourgoin with 13 tries on the way to a 92-17 victory and Benetton Treviso's 29-23 home win over Bath Rugby added up to Leinster going four points clear of the Italian champions with their showdown set to come in Italy in Round 6.
The return of their international stars certainly gave Leinster a big lift and Kidney believes more sessions together this week will see another improvement.
"You have to work with what is under your control and the challenge comes when your international players are away and just how long it will take for them to click back in," he said.
"In that respect some aspects of our play were very good and a lot of the guys had good moments. But there were also some poor moments and what I am after is great consistency and that is something I hope we will show over in France in Round 4."