Takayuki Kishi was pulled partway through the third inning against Rakuten on April 24 because of discomfort in his right leg. He was examined at a hospital in Tokyo on April 25 and diagnosed with a right adductor injury that will require about a month for a full recovery.
Source: Daily Sports 4/26/2016
[UPDATE 4/27 @ 11:28pm]
Kishi will need at least one month for a full recovery. The Lions do not want to rush him and could give him an extra month. They might be looking at a return some time around the end of Inter-league play.
Source: Sponichi 4/27/2016