The Sunwolves are under no illusions about what they must do Saturday to beat the Melbourne Rebels in their second game of the Super Rugby season — stop Amanaki Lelei Mafi and Will Genia.

Japan international No. 8 Mafi was the Australian Super Rugby player of the year in 2017, while Wallabies scrumhalf Genia showed last week in the 45-19 win over the Reds that he is back to his very best.

"(Mafi) is well known to the Japan boys and a very good player," Sunwolves defense coach Scott Hansen said Friday at Prince Chichibu Memorial Rugby Ground. "Last year he had a huge influence in Super Rugby in terms of carry meters and we will have to limit his opportunities to influence the game."

Genia, meanwhile, "has influenced world rugby and referees for a long time," Hansen said. "We will have to defend well around the fringes and we will have to be smart how we organize our defense around him. We have definitely talked about him this week."

Mafi and Genia are part of an unchanged starting XV for the Rebels, who have a number of players with experience in Japan in Dane Haylett-Petty (Toyota Industries Shuttles), Geoff Parling (Munakata Sanix Blues) and Jack Debreczeni (Honda Heat).

"It's always good to get that first game out of the way and to get a good win," said Rebels assistant coach Joe Barakat, who had spells coaching the Toshiba Brave Lupus and the NTT Communications Shining Arcs.

Barakat said the area in which Mafi and Genia excel, more than any individual player, would be critical to the outcome of the game.

"It's key to any team's success," Barakat said of the fringes around the breakdown. "The level of physicality in the game is going to be key to success as well. They (the Sunwolves) want to play a brand of rugby that moves you around and goes coast to coast. We need to be a little bit different to that, and control of the ball will be crucial."

By contrast to the Rebels' stability, the Sunwolves have made six changes and two positional switches from the side that lost 32-25 to the Brumbies.

"We understand they are very different from the previous week but we have to be concerned about how we play the game," Barakat said.

Michael Leitch is set to make his Sunwolves debut following three years with the New Zealand-based Chiefs, and the Japan captain said he was raring to go.

"I think I am in (the side) as the result of injuries rather than form but I am starting to feel good," Leitch told Kyodo News. "I haven't felt this good in a long time, so I am pretty excited about going out there tomorrow.

"I'm getting my ball in my hands a lot more now so once I get it I have to do something with it."

Leitch lines up with Ed Quirk and Lappies Labuschagne in the back row, with the latter having made and completed 22 tackles last week.

"Our philosophy in defense is to look after one another," said Hansen. "The mindset is to get the ball back so we can attack, but you can't get away from what defense is all about. At the end of the day it's about making tackles."

The two sides have met just once before in March 2016, with the Rebels winning 35-9.

But Leitch believes the Sunwolves showed enough in last week's opener that they are no longer the easybeats of the competition.

"For a side that had no warm-up game, we put in a good performance against a quality side," Leitch said. "I'm looking forward to what we have to offer tomorrow."