The culprit is reportedly a Grade 2 sprain of his right MCL, which happened during training last week. This is the same injury that kept him out of contention for the away game at Minnesota United, which the Fire lost 2-1.
In his stead, the Fire will likely continue to rely on Rafael Ramos to fill his spot in the wide defender role.
Polster is now the seventh Fire player currently on the injured list. Of those seven, five of them are defenders— Polster, Christian Dean (right foot), Jorge Corrales (infection), Jonathan Campbell (facial fracture), and Grant Lillard (right knee). Needless to say, the next month or two is going to be quite an ordeal for the Men In Red.