Daiki Asama ended practices early on February 7 (Arizona time) because of lower back pain. He is considered day-to-day.
Source: Sanspo 2/9/2017
[UPDATE 4/5 @ 7:17pm]
Asama worked out at the Kamagaya facilities on April 4. He is scheduled to participate in a batting practice scrimmage on April 9. Assuming no issues, he could play in his first rehab game at Ni-gun on April 11.
Source: Nikkan Sports 4/5/2017