Ryosuke Hirata hurt his right shoulder while chasing after a baseball in the fifth inning of a game against the Hiroshima Carp at Nagoya Dome on September 13. He was replaced on defense in the 6th inning.
Hirata was taken to a hospital in Nagoya for tests and diagnosed with a minor right shoulder labrum injury. He later told reporters that he first started feeling pain in his shoulder about half a month ago. He was able to play through the pain, but it got worse, to the point where it was throbbing when he stood. He will most likely be taken off the active roster on September 14 and will be shut down for about a week. He might end up missing the rest of the season.
[UPDATE 9/14 @ 7:41pm]
Hirata told reporters that he suffered the same injury during his third year in high school (September 2005). He also admitted that the injury affected his swing.
Source: Sports Hochi 9/14/2016