Sanderson admitted a failure to execute the game plan had cost the team, but insisted they could win the return match in Montpellier and still progress from the pool stages.
"It's all a bit raw at the moment, there is a lot of emotion flying around, it's not the result or performance we wanted," he said.
"It wasn't a great night for us and that is, primarily, because we didn't execute the game plan. Because of that we lost the game - it is not difficult to put right.
"We're deeply disappointed. We now have to win away in Montpellier to get out of this group.
"We have won away in France before and we can do it again, but right now there is a lot of emotion and we need to keep a lid on it and look at next week.
"We have an away game in Madrid now to focus on and we have got to put it right then."