"You wouldn't consider any match against a team of Island rugby players as an easy opener to a Test series.
"I know the scoreline in some of our matches has been heavily in favour of the opposition by the closing stages.
"That is down to the short time we have to prepare, but we are able to compete strongly as we will show against England."
Shane Geraghty, part of the England elite squad for the November Tests which also include games against Australia, South Africa and New Zealand, knows the strengths of his Exiles team-mate well.
"You don't want to have to face his Samoan sidestep," said Geraghty, in reference to the Islanders' love of running over, rather than around opponents.
"Playing alongside some of the guys in the Islanders squad, I know how tough this match is going to be at Twickenham. This is the first Test of a new England era and I am sure the Islanders will challenge us in every area at the start of an exciting month."
Mapusua insists that despite the ad hoc nature of their selection, a Test class showing is possible on Saturday.
"There is a lot of talent in the Islands," he said. "But, for years, there has been a lot of talk about not enough resources going into rugby in the Islands.
"That's why the players have moved to Europe and Japan to earn a living.
"We just want to be operating on a level playing field so that when we take on other nations we are given the best possible chance.
"If that does happen then I can promise you quite a few upsets."
And he is sure the team will make the most of their opportunity on Saturday. "You are proud to play for Fiji, Tonga and Samoa and then hope to get picked for the Islanders squad," he added.
"That is great for Island rugby and will make players try even harder because the tours only come around every two years."
Tickets for the game are still available from www.ticketmaster.co.uk
