An option that would make a lot of sense offensively would be to throw Takehiro Donoue out there, he was originally a first baseman before being moved to the outfield. T. Donoue doesn't really have a place in the outfield right now and has swung the bat well in limited time, so it would be worth a shot.
We will see what Takagi goes with, so far while I haven't really liked a lot of Takagi's comments in interviews, he does seem to make pretty solid decisions as far as playing time.
Until Masahiro Araki comes back which could be a couple more weeks or more, hamstring injuries seem to linger, I would keep Naomichi Donoue at 2B, Morino at 3B, and do a bit of a platoon with T. Donoue and Diaz at first to see if one can play themselves into the job. Yamasaki would remain as the veteran bat on the bench. Then once or twice a week I would play Morino at 1B and Takahashi at 3B. One thing is for sure, this team would be in serious trouble if they had another injury on the infield right now.