Japan suffered a blow Thursday when playmaker Shinji Kagawa was ruled out of next week's World Cup qualifier against Iraq after dislocating his shoulder.
The Borussia Dortmund midfielder fell awkwardly in the 1-1 friendly draw with Syria in Tokyo on Wednesday, a warm-up for Tuesday's match in neutral Iran.
The Japan Football Association (JFA) said it would not call up a replacement for Kagawa, who was stretchered off after just nine minutes.
"I want to concentrate on healing the injury as quickly as possible," Kagawa said in a statement.
The JFA said the Blue Samurai will travel to Tehran on Thursday as planned, despite Wednesday's deadly terror attacks in Iran's capital.
Gunmen and suicide bombers stormed the country's parliament and the shrine of its revolutionary leader, killing 12 people in attacks claimed by the so-called Islamic State.
Japan currently top Asia's Group B from Saudi Arabia on goal difference with Australia three points behind. The top-two qualify automatically for Russia 2018 with the third-place team entering playoffs.