He also praised the Carbery, Henshaw, Ringrose combination
Leinster head coach Leo Cullen is pleased with the result against Castres but admits that there is also a small layer of frustration that they couldn't be more clinical.
The province opened their European Rugby Champions Cup account for the season with a 33-15 bonus point victory over the visiting French side at the RDS.
Speaking to Newstalk Sport's Cian Murtagh after the match, Cullen shared his satisfaction but also flagged areas of improvement for his team, including being able to make the most of the many chances that they created.
"I thought we created a lot of opportunities. We're pleased with the outcome, result and all that but it's almost a bit of frustrating as well. We could have been a little bit more clinical at times," he said.
"But conditions were tricky at times as well, obviously with that pretty big downpour just after we scored that first try. Anyway we'll move on. Different challenge next week against Montpellier but it's a good start - better than this time last year."
Joey Carbery (20) made his European debut in the No 10 jersey and Cullen was pleased with his performance.
"There's some pretty big French players there. He's got really good footwork and he's got that level of bravery to take the line on as well so I think you've seen it over the course of pre-season and some of the early Pro 12 rounds as well. He's on a very positive curve," he said.
Cullen is also confident that the young triumvirate of Carbery, Rob Henshaw and Garry Ringrose will only get better as the trio who are 20, 23 and 21 started together at out-half, inside-centre and outside-centre.
"With Robbie and Garry, it's a very young 10, 12, 13 axis there. But they're going to improve and they're going to get better and it's an exciting prospect," said Cullen.