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

Chile will be making its World Cup debut on Sunday when the side runs out against Japan, the host of the 2019 edition that won all four of its 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.