Albirex Niigata were dealt a blow on Friday after they sent club top scorer Rafael Silva back to Brazil to treat a torn right hamstring.
The 23-year-old will require up to six weeks to recover from the injury which was sustained during training on July 9.
Rafael joined the club in mid-2014 and has been Albirex’s main source of goals this season, netting seven times in 12 appearances.
Masaaki Yanagishita’s men were nevertheless able to do without their talisman on Sunday as they overcame Sagan Tosu 1-0 thanks to Kei Koizumi’s stunning volley.