Canada are tipped to challenge tournament hosts England for the title.
Wales have not beaten them since their 2006 triumph in Cardiff, with their last meeting a 42-22 defeat at WXV1 in New Zealand two years ago.
“They are a very physical team, they are second in the world, they are up there with some of the favourites to win this tournament,” said Crabb.
“But for me personally and I think as a team, that makes us really excited, because, yes, we are the underdogs, but we have also got nothing to lose.
“We have got everything to gain because we are really disappointed in the way that we portrayed ourselves as a team at the weekend.
“We have not put all the hard work in that we have, and got to the place where we’re at as a team, to not show that when it matters most on the pitch.
“We have to find a way to get to those quarter-finals and this weekend is going to play a huge role for that, so we’ve just got to go after it.”