Rugged defense and an ability to steal opposition ball have been behind Japan's run to a possible place in the quarterfinals of the Rugby World Cup.

And nobody has epitomized that more than Jack Cornelsen.

Japan's Jack Cornelsen (C) makes a tackle against Chile during their Rugby World Cup pool-stage match in Toulouse, France, on Sept. 10, 2023. (Kyodo) 

The son of Wallabies legend Greg, who is in France watching his son play, Cornelsen junior has been dubbed the "Silent Assassin" by the father of one of his teammates for all the work he has put in, whether it was playing at No. 8 against Chile, when Kazuki Himeno was a late withdrawal, or in the second row.

"To be honest there is not much change if I'm playing second or back row, as I'm normally in the middle of the field," Cornelsen said ahead of Sunday's crunch game with Argentina.

"I think my job is just to get involved as much as I can to do my job for the team."

Japan head into the final weekend of pool play knowing they must beat Argentina -- or score four tries in a draw and prevent the Pumas from doing the same -- if they are make the last eight for the second-straight tournament.

"There's not that much change for us in terms of how we want to play, but we know that this is a must-win game for us if we want to go to the quarterfinals," the 28-year-old Saitama Wild Knight said.

And while the Brave Blossoms will look to run the Pumas off their feet, they know that, as in most games, the battle up front will be key.

"Starting at set piece is going to be a really big one for us," Cornelsen said.

"Obviously they are a very passionate team, big players and big ball carriers. So we know that they want to use that to their advantage and go forward to get momentum."

Cornelsen comes into the game having made 44 of 48 tackles and has yet to concede a penalty. He has also won 10 line-outs, and stolen five opposition throws at the set piece (the joint most at the tournament). And he admitted the Brave Blossoms had worked hard this week on ensuring everyone is on the same page.

"We know that their best strength is playing off set pieces, so being able to disrupt them there, and not let them have momentum and get into their game," he said.

"When we get a chance to attack, just being able to play freely, play our Japan rugby and try to put them on the back foot, really."

Easier said than done, but Cornelsen has shown he does not just talk the talk, he walks the walk as well.


Related coverage:

Rugby: Fifita in to face Pumas as Japan make just 1 change

Rugby: Brave Blossoms' "One Team" concept alive and well in France

Rugby: "Genki" Brave Blossoms bid adieu to Toulouse as Pumas await