Japan players on Friday acknowledged criticism of the tactics that saw them settle for a 1-0 loss against Poland the previous day, but said they were simply doing what was needed to secure the Samurai Blue's first World Cup knockout-stage berth since 2010.

The squad returned from Volgograd by charter Thursday night to their World Cup base in the southwestern city of Kazan after becoming the first side to reach the round of 16 thanks to the "fair play" tie-breaker introduced this year.

Down 1-0 late in sweltering conditions at Volgograd Arena, Japan opted to hold onto the ball and avoid any attacking forays that might risk a booking or another Poland goal after learning that Senegal was also trailing 1-0 against Colombia in the other Group H match being played simultaneously.