I think Jana's on-court performance (by itself and in comparison to Serah) has reached the point where Geno needs to consider replacing Serah with Jana in UConn's starting lineup. Moreover, I think Geno may be thinking along those lines also, based on his "quick hook" for Serah in recent games when she makes mistakes.
Neither player is a reliable scorer from the center position, but at least Jana is a reliable rebounder. And she seems to have gotten her fouling tendencies under some degree of control.
I do worry, as I bet Geno does, about the effect on Serah's frame of mind if she is demoted to the bench. As a senior, she needs all the minutes she can possibly get to advertise herself to WNBA scouts. But of course, that can't be Geno's top priority at this time in the season.