The Leinstermen have responded to adversity before but a difficult European pool that also contains champions Toulon just got that much harder.
Matters were not helped by captain Isa Nacewa pulling out just before the game and Cullen says Leinster, who have won five games out of seven in the GUINNESS PRO12 so far, must right some wrongs next weekend.
"(The defeat) leaves us scrambling," said Cullen, who saw his side fall to just a third defeat in their last 15 European games.
"We've been in the situation where we've lost our opening pool game and qualified, but it's going to be tough. We can't look beyond Bath now.
"You force things - you see experienced players making uncharacteristic mistakes and it's really frustrating.
"They guys prepped really well before the game, we had a few late injuries, but we should still have been good enough on the day.
"Credit to Wasps, they came with a very simple gameplan. They took their opportunities when they arose. It's very disappointing because I know we can be a lot better than that."
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