Robin McBryde is without 15 frontline players, who are touring with the British & Irish Lions, and a host of other players have been left at home due to injury and necessary rest.
And McCusker knows all to well that Wales must hit the same standards in the Far East as they did in their Championship winning campaign.
“Wales have not conceded a try in four-and-a-half games. We’re not in any rush to let that slip,” said McCusker, 27.
“It’s our careers at stake here with potential [future] Welsh spots up for grabs so we’re going for it.”
Japan warmed up for the visit of Wales with a 27-17 defeat to Tonga and they face Fiji tomorrow.
Despite the loss, Wales were impressed with Japan, in particular their driving lineout and McCusker is well aware of the threat posed.
“We’re wary across the board, but we’re not setting ourselves up for a fall at all,” said McCusker
“Intrinsically we’re expecting two wins and two good performances.
“There’s a lot of pressure on us from the coaching squad and what we’ve put on ourselves as players to carry on the mantle from a championship-winning Six Nations.”
In preparation for the difficult hot and humid conditions expected in Japan, Wales turned up the heat and sanded balls down at their training base.
“It’s pretty uncomfortable, but we’ve got to realise that it’s probably only half as hot as it’s going to be in Japan,” said McCusker.
“Plus you can’t really replicate the humidity in there. I’ve played in Hong Kong in the Sevens and that’s a pretty similar climate.
“It definitely takes your breath away and I just think we have to bite the bullet when we get there.”
