Leinster flanker Shane Jennings has conceded how strange it was to go from thrashing Northampton to losing at home.
Saints produced an impressive turnaround last Saturday through a performance of raw power, as they shut down the three-time champions in a 18-9 win.
A win would have seen Leinster open up an almost insurmountable eight-point gap at the top of Pool 1 over their rivals, but now with Northampton back in the mix they have work to do.
"We're realistic about the whole situation. It's massively disappointing," Jennings told The Irish Times.
"We're at home in a European game and they're the games you really go after. Obviously we took a lot of confidence from the week before.
"It was a bit strange the way it all clicked [in the 40-7 win at Franklin's Gardens]. But this week it didn't click.
"It's the obvious statement, but it's so disappointing that you can't reproduce that performance against the same team."
Now looking ahead to a busy festive period when Leinster will take on Edinburgh, Ulster and Connacht before returning to the Heineken Cup against Castres, Jennings is looking for a lift from the squad.
"It's a big old Christmas period for us starting this Friday and then a couple of inter-pros leading into Europe again," added Jennings.
"Big games for the club and there are going to be a lot of players coming in and out. So we've got to show that we've a good squad and the ability to go over to these places and perform."