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.

Japan came into Thursday's encounter tied at the top of Group H with Senegal on four points and with an identical number of goals and goal difference. They needed a draw with Poland to guarantee a trip to the knockout stage.

Failing that, they needed to finish their third match with fewer fair play points -- calculated based on the number of red and yellow cards accumulated -- than Senegal should they not be able to be separated through all the other criteria.

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 were also trailing 1-0 against Colombia in the other Group H match being played simultaneously.

The tactic elicited loud jeers from the stands, as well as criticism from some Japanese fans afterwards. However, the decision to hold on for the 1-0 loss proved the right one under the circumstances, right back Hiroki Sakai said Friday.

(Spectators boo as Japan players pass the ball around for possession against Poland)

"I think (the criticism) is normal. Anyone in any profession can expect the same. But those who are adamant that (holding on for a 1-0 loss) is unacceptable would understand better if they were in our position," the Marseille defender said.

"Although we were all in it together, there were probably some differing opinions (among the team). But that's irrelevant now and looking back isn't going to change the result."

Sakai, who is reportedly a target of English Premier League side Crystal Palace, said he was not surprised when Japan coach Akira Nishino sent captain Makoto Hasebe into the game in the 82nd minute with instructions to "stick with 1-0 and don't pick up any yellow cards."

"I thought there was a chance that such a message would come," Sakai said.

Attacking midfielder Takashi Usami, who made his first start of the tournament against Poland, said although it was hard for some players to accept settling for the loss, it was necessary to avoid jeopardizing Japan's path to the round of 16.

"It was a difficult situation for us to (play for the 1-0 loss). But that's just the way it ended up," Usami said.

"I've never experienced anything like the last 10 or 15 minutes of that game. I think it could only happen at the World Cup."

Japan will face Belgium in the round of 16 in Rostov-on-Don on Monday, with the winner progressing to a quarterfinal against either Brazil or Mexico in Kazan.