Kodai Senga got the start against the Orix Buffaloes at Kyocera Dome tonight, but he developed discomfort in his back and left after recording two outs on nine pitches (fly out to right on one pitch, strikeout swinging on eight pitches). He was taken to a hospital in Osaka for tests.
[UPDATE 5/17 @ 9:45pm]
The Softbank Hawks decided not to take Senga off the active roster for the time being. They will adjust his pitching schedule based on how he is feeling over the next day or two. Tests (MRI, CT scan, x-rays) conducted at the hospital last night did not reveal any serious issues.
[UPDATE 5/18 @ 5:35pm]
The Hawks announced on May 17 that Senga has tightness in the left side of his back.
Source: Sanspo 5/18/2017
[UPDATE 5/20 @ 4:40pm]
Senga resumed practices on May 19. He did some running and played some light catch at a distance of about thirty meters.
Source: Nikkan Sports 5/20/2017
[UPDATE 5/21 @ 3:02pm]
The Hawks are not planning to take Senga off the active roster for the time being, even though he will most likely miss his next scheduled start (May 23).
Source: Sponichi 5/20/2017
[UPDATE 5/23 @ 12:15am]
Senga was scratched from his start on May 23. He will now get a start during the Nippon Ham series at Sapporo Dome that begins on May 26.
Source: Daily Sports 5/22/2017
[UPDATE 5/24 @ 9:27pm]
Senga tossed a bullpen session at YafuOku Dome today. He threw forty pitches to a squatting catcher. He will toss another session on May 26. Assuming no problems, his next start could come on May 28 against Nippon Ham.