Japan coach Hajime Moriyasu has an anxious wait on the fitness of star forward Kaoru Mitoma before naming a World Cup squad on Friday.
Mitoma limped off with an apparent hamstring injury Saturday in the second half of Brighton's 3-0 win over Wolverhampton in the Premier League.
One of Japan's standout players at the 2022 World Cup, Mitoma scored in a 1-0 win over England in March at Wembley Stadium.
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His World Cup tournament is in doubt five weeks before Japan face the Netherlands on June 14 in Arlington, Texas.
"I hope it's a minor injury. I was told by staff, 'It doesn't seem minor,'" Moriyasu was reported telling Japanese media Sunday about Mitoma.
Brighton coach Fabian Hurzeler said "it looked like a hamstring injury" but the club would await scan to clarify the severity.
Seventh-place Brighton are still in contention to qualify for the Champions League with two rounds left in the Premier League. England could get a record-tying six entries.
Japan's World Cup plans are already missing another key forward Takumi Minamino, who tore an ACL playing for Monaco in December.
Japan also play Tunisia on June 20 in Monterrey, Mexico, then return to Texas to play Sweden on June 25. The top two in Group F advance to the round of 32 and the third-place team also could join them.