Girgensons (undisclosed) didn't return to Saturday's game versus the Mammoth after getting hurt in the second period, Benjamin Pierce of the Lightning's official site reports.
As is typical with the Lightning, there was no update on Girgensons' status after the contest. He'll have longer than usual to heal up, as the Lightning's next game is Thursday versus the Jets. If he's unable to play, Dominic James would likely re-enter the lineup after being a healthy scratch Saturday.