Victory over Fiji at the Millennium Stadium in Cardiff would see them go top of Pool A.
Head coach Warren Gatland says the fact their opponents are without a win so far in the tournament doesn't mean his side are assured of coming out on top.
Meanwhile, the England team for their latest rugby union World Cup match is announced later.
They play Australia at Twickenham on Saturday, with a loss potentially ending their chances of reaching the quarter finals.
Jonathan Joseph is being tipped to return to the team, replacing Sam Burgess at centre, while Ben Morgan is also poised for a recall, and Joe Launchbury may earn his first start of the tournament.
