The media learned on October 21 that Yamato will have surgery on his left ankle. He is expected to be ready for spring camp next year.
Source: Sports Hochi 10/22/2018
[UPDATE 10/31 @ 11:23am]
The Bay Stars announced that Yamato had surgery to clean his left ankle at a hospital in Yokohama on October 30. There were no complications during the procedure.
Yamato originally hurt the ankle during practices before a Yakult game at Yokohama on September 8.