Hayes (upper body) has been downgraded to week-to-week by coach Mike Sullivan, per Michelle Crechiolo of the Penguins' official site.
Hayes has already missed the Pens' last two games with an upper-body injury, and it appears he could be slated for an extended absence. The 32-year-old Hayes had three goals and four points in his first 14 games with Pittsburgh. Blake Lizotte figures to remain in the lineup in Hayes' absence.