The Astros placed Imai on the 15-day injured list Monday with right arm fatigue.
Imai recorded just one out in his last start and looks to be going through a "dead arm" phase. The right-hander will be eligible for activation before the end of April, but it's unclear at this juncture whether he will be ready to go by that time. Houston's rotation depth is really being tested, as Imai joins Hunter Brown (shoulder) and Cristian Javier (shoulder) on the 15-day IL. The club also has Ronel Blanco (elbow), Hayden Wesneski (elbow) and Brandon Walter (elbow) on the 60-day IL.