Leinster left it agonisingly late again, snatching victory in France yesterday by the smallest of margins.
In a tough, physical game that only saw one try and a general lack of backline creativity, Leinster's experience in Europe eventually shone through. They did have to rely on an ounce of luck though, as Castres will kick themselves.
Leinster were certainly not at their best but they will be delighted that in the crucial last few minutes of the game and leading they did control things a lot better. Winning becomes a habit just like losing does, and Leinster simply know how to win tight games, Castres don't.
Leinster didn't play well, but they ground the opposition down and with all their injuries, they will feel that they have now pulled two games out of the fire. They can now, hopefully, get some key players back and get considerably stronger.
It sets up a mouth-watering home and away series against Harlequins in December. And at this stage, you feel those games could decide the outcome of this pool?
Obviously, Castres were lying in the long grass for Leinster, especially given that the Dublin based side were the only team to lower their colours on home soil in 2014. Leinster had a real chance to throw down a pre-Christmas marker, and take a serious confidence booster into the home and away fixtures against Quins in December.
But they didn't start the game like that. For Castres, it was perhaps their last chance to stay in this competition, and if they weren't up for this game in a newly renovated stadium, than it probably meant that they were not really interested in European rugby full stop.
Castres certainly did not start as if they were not interested in competing in Europe, using serious muscle up front, intelligent decoy runners, wingers coming off their wings and good overall game management from their captain and out-half Remi Tales.
Just as they did last year, Castres raced off to an early start, courtesy of a simple pushover try. Once again, Leinster had let the opposition team in for early points far too quickly.
But, just as they did last week against Wasps, Leinster soon started to do what they do best, using their dynamic ball-carriers like Sean Cronin and Jamie Heaslip out wide and allowing them to get their backs onto the front foot.
Leinster just needed to hold onto possession a lot better than they did - especially in the opposition red zone with the Castres forwards easily turning over the first three forays Leinster made into their 22.
With too many mistakes in key areas, and a big defence from Castres, Leinster found it hard to get any real dominance in the game, despite an overwhelming advantage in both possession and territory.
At times, the visitors also looked a little too predictable in their game plan, especially with their inside-fed balls from outhalf Jimmy Gopperth being fairly well telegraphed.
The problem for Castres was the number of tackles they were being forced to make, especially in the first half, and on a hot day and with their bigger bodies, the longer Leinster could deny Castres the ball and remain patient, the better chance they would eventually win this game.
With the score 9-7 at the break, it was clear to see what was happening. Castres were relying on a huge scrum and an aggressive defence to stay in the game, while Leinster were trying to dominate the ball, speed up the game up and keep the play away from the fringe areas. In a nutshell, force Castres to fatigue and then try and break the game up.
Leinster imploded early in the second half, going to ground far too early and giving away silly and punishable penalties. More significantly, they were letting an inferior side back into the game.
Leinster were also missing the crucial first-up tackles, especially on big Castres winger Remi Crossou.
But you still had the feeling that Leinster knew that if they didn't panic and kept within one score of the opposition, then they had it in them to win.
French fitness levels often seem to be the most questionable in the European game. In the last few minutes Castres had the ball, but instead of pinning Leinster back with a sensible kicking game, they allowed the visitors to force territory for the game-winning penalties.
Once again, it was the Leinster forwards who shone.
Sean Cronin was the outstanding ball-carrier, alongside Jamie Heaslip, while Devin Toner worked hard on his set-piece duties.
Leinster will be delighted - two games, two wins, still winning ugly but winning nonetheless. They will take that.