Japan will not be taking their World Cup Pool D opener against Chile for granted, defence coach John Mitchell warned Tuesday, saying the South Americans were a well-coached, cohesive unit.

Chile will be making their World Cup debut on Sunday when they run out against the Japanese, the hosts of the 2019 edition who won all four of their pool games, notably taking the scalps of Ireland and Scotland.

"Chile, while it is important to focus on ourselves first, they are a very gritty side," Mitchell said.

"They have showed determination to get entry into the World Cup and in all their warm-up games they have demonstrated real cohesiveness and ability to fight for each other.

"They are also sprinkled with an outstanding 10 who is very attacking and a 15 who is also very attacking. Naturally they have their direct players, their nine is a very good runner of the ball."

Mitchell highlighted as crucial for Chile the presence of coach Pablo Lemoine, who made 48 appearances and featured in two World Cups as a prop for Uruguay.

He was appointed in 2018 and has overseen Chile's route to qualify for the tournament, including two-legged play-off wins over Canada, ever-present since the inaugural tournament in 1987, and the 2031 hosts United States, denying both of them a place in France.

"They are coached by a very experienced coach in Pablo who also got Uruguay to qualify for a World Cup in 2015, he comes with enormous experience," Mitchell said.

"He will be working on the need to remain calm under pressure because this tournament bring different pressures."

- 'Costly for us' -

Japan are ranked 14th in the world, below Argentina, former winners England and an improving Samoa in their pool, and lost three of their four warm-up games, finishing with a 42-21 defeat by Italy.

But Mitchell said those matches were treated as an opportunity to mix things up.

"The warm-up games, as much as you want to win them all, we tried different things, we tried different selections. We were working on some things that needed to be fixed and grow as a team,” the former England coach said.

"The Italy game, we thought our ability to push through to front door from back-door attack was something we needed to grow, it was something we didn't deal with early in the match and just after half-time. That was costly for us."

Japan received two red cards for dangerous tackles in their warm-up games and Mitchell said the team had "addressed that by slightly changing our technique".

"We will still continue to hit through the ball and under the ball," the Kiwi said.

"So it's really much more on the adjustment of the height by dipping on entry and that goes in conjunction with your lead foot.

"We have got to be very aware of it (high tackles). But I think we are at a stage now where it is not a surprise to us."

bur/lp/pi