Leinster head coach Matt O'Connor was adamant his side was not complacent as Northampton dented his side's chances of a home Heineken Cup quarter-final.
Saints held Leinster tryless in front of a big home crowd at the Aviva Stadium, as tries from George North and Jamie Elliott spurred them to a deserved 18-9 Pool 1 victory.
It came just a week after O'Connor's charges thrashed Northampton 40-7 at Franklin's Gardens and their first European defeat of the season leaves them with a sour taste the the mouth entering a busy Christmas period of league fixtures.
"We were inaccurate. We didn't look after the ball as well as we would have liked," admitted a disappointed O'Connor.
"We certainly didn't look after it as well as we did last week. That let Northampton into the game. They went out in front (leading 7-3 at half-time) and to be fair they played the upper hand quite well.
"They were playing for pride for a large part of it. We understood that. We knew they would come back at us and I think the defence at the end (from them) summarised the massive effort throughout the game.
"They kicked it into the corners and drove and made it hard for us to get any field position in the game and off the back of our ill-discipline and penalty count they had opportunities to do that.
"That was our fault. We didn't control possession and didn't get field position and we probably didn't put them under enough pressure. We talked a lot about that during the week but there wasn't a complacent edge to us. We were just inaccurate off the back off their commitment."
Samu Manoa, Courtney Lawes, Christian Day and Tom Wood all had big games up front for Northampton who twice had their lead cut to a single point - 7-6 and 10-9.
A Kahn Fotuali'i drop goal and Elliott's intercept try in injury-time sealed the victory and with Saints now four points behind leaders Leinster, their director of rugby Jim Mallinder feels there is still plenty to play for.
"It gives a little bit of life to the group. It's not sort of dead and buried. We still got two tough games, but Leinster have got that as well," he said.
"It gives us hope and it is still great to be in the competition with something to play for and it sets us well for the next few weeks in the Premiership.
"It is definitely one of the good wins. You don't get many wins away from home in the Heineken Cup. You certainly don't get many wins against a quality side like Leinster. And they are still a quality side. Just because we beat them doesn't put them down in my estimation."
His opposite number O'Connor believes his team are still where they want to be with their destiny in their own hands.
"We've got two really tough games, one against Castres away and then we got Ospreys at home. You've got to win those two games.
"They were games that we would have looked at at the start of the group and would have said we wanted and had to win those. It hasn't changed dramatically. We just have to make sure we are at the very top end of our game whenever we play."