Japan manager Akira Nishino has warned his players that there is still plenty of work to do if they are to seal a place in the last 16 of the World Cup.
The Samurai Blue took a big stride towards progressing from Group H on Tuesday afternoon by beating Colombia 2-1 in their opening match.
Shinji Kagawa and Yuya Osako netted either side of Juan Quintero's equaliser as Japan capitalised on an early red card shown to Carlos Sanchez.
Japan's players celebrated their victory on the Mordovia Arena field after the match, but Nishino acknowledges that there are still tricky tests to come against Poland and Senegal.
"I said at half time that if we can keep the ball moving, we can deprive the Colombia players of their stamina," he told reporters after the match.
"Our players were aggressive from the start and I think that worked very well for us. This is just one win and three points, so we will save our celebration."
Japan had never previously won a World Cup game on European soil in six attempts.
