The Fiji sevens team can seal back to back World Series titles on day one of the London tournament at Twickenham.
While Samoa are hoping to build on their stunning performance in Paris.
Ben Ryan's side have made all the headlines this week after the shock addition of Jarryd Hayne to their playing squad.
The 28 year-old has set his sights on playing at the Rio Olympics but can also help Fiji wrap up another World Series crown later tonight.
They lead South Africa by 14 points in the Worlds Series standings and Ben Ryan said the equation for his team was simple.
"The quarter finals is all we need to win the World Series. We've topped every pool we've played in so far this year. Even with the occasional loss in the pools we've still won the last nine pools. "
"If we do that we'll hold the World Series and be the first Fijian team to win back to back. We have a very tough pool: Australia will make six changes, England will make four and Wales in Europe are hard so we can't get carried away or assume anything is going to happen other than three hard games," he said.
Meanwhile Samoa have been buoyed by their stunning win in last week's Paris Sevens.
The Manu beat Fiji in the Cup final and could do their Pacific rivals a favour if they beat second-placed South Africa in the pool stage overnight.
Samoa also face USA and Canada on day one and, not for the first time this season, coach Damian McGrath will be undermanned.
"Alamanda Motuga dislocated his shoulder (in Paris) but given the length of time to get someone here we're going to keep Alamanda with us for treatment and just go with eleven (players)."
Damian McGrath said they just want to get through this tournament relatively injury-free so they can concentrate on their main target this season, qualifying for the Olympics.