Stefen Romero crashed into the wall padding in foul territory while attempting to catch a ball in the bottom of the eighth inning. In the process, he slammed his left knee in the base of the wall. He had to be carried off the field on a stretcher. He was taken to a hospital in Chiba for tests.
[UPDATE 4/22 @ 10:52pm]
Romero had x-rays and an MRI. He was diagnosed with a bruise on his left knee. He is considered day-to-day for the time being.
Source: Sports Hochi 4/22/2017
[UPDATE 4/23 @ 6:43pm]
Romero did not play today and returned to Kobe. He will be re-examined at a hospital in Kobe on April 24.
[UPDATE 4/25 @ 12:48am]
The Buffaloes announced on April 24 that Romero was examined at a hospital in Kobe and diagnosed with bone contusion in his left femur (knee).
[UPDATE 4/25 @ 6:55pm]
Romero was taken off the active today. He will most likely require about four to five weeks for a full recovery.
[UPDATE 5/5 @ 5:29pm]
Romero started taking batting practice against a pitching machine on May 4.
Source: Nikkan Sports 5/5/2017
[UPDATE 5/16 @ 5:52pm]
The media learned on May 15 that the Buffaloes still have no timetable on Romero’s recovery. Based on original estimates, he should be getting ready to play in his first rehab game soon, but his workouts are still being set/closely monitored by team trainers.
Source: Sports Hochi 5/16/2017
[UPDATE 5/23 @ 6:51pm]
The Buffaloes might leave it up to Romero to decide whether he needs to play in any rehab games at Ni-gun before he returns to the active roster. They feel his presence on the active roster alone (so long as he can either be a designated hitter or a bat off the bench) might help give the team a boost in the right direction.