Japan coach Vahid Halilhodzic is facing an injury headache ahead of Thursday's vital 2018 World Cup qualifier against Australia after defender Yuto Nagatomo limped off the pitch during Inter Milan's victory over Roma over the weekend.
With 91 caps since 2008, the left-back is one of Japan's most experienced and consistent performers.
Just before the hour of the 3-1 win at Roma's Olympic Stadium, Nagatomo asked coach Luciano Spalletti that he be substituted.
According to the 30-year-old, he felt some discomfort after half-time and couldn't run freely.
"My hamstring tightened up," Nagatomo said. "I'll head home and talk things over with the doctor."
The former FC Tokyo star, who moved to the San Siro in 2011, is scheduled to arrive in the Japanese capital on Monday evening and will then be examined by staff.
As well as the crunch game with the Socceroos, Japan face a tricky trip to Jeddah in the final Group B game, to face Saudi Arabia on Sep. 5.
Halilhodzic's men top the group, ahead of Australia and Saudi Arabia by a point. They will qualify for a sixth successive World Cup with a win at Saitama Stadium on Thursday.
A draw or defeat against the defending Asian champions will likely mean, however, that Japan will have to get a result in West Asia five days later.
Halilhodzic, appointed in 2015 after leading Algeria to the knockout stage of the 2014 World Cup, has been under pressure. Reports in Tokyo last week, dismissed by the Japan FA, were that he could be fired if Japan fail to defeat Australia.
There was better news for the Bosnian from Germany. Striker Yuya Osako, who has been recovering from injury, played 90 minutes for FC Koln in a 3-1 defeat at home to Hamburg.
Only the top two teams from Group B qualify automatically for Russia 2018. The two third-placed teams from Asia meet in a two-legged tie in October for the right to take on CONCAFAF's fourth-placed nation in a final play off.