Ospreys flanker Tom Smith looks set for another lengthy spell on the sidelines after injuring his knee against Edinburgh.
Smith had only just returned from a year out of the game with a groin injury and he had to be stretchered off after falling awkwardly in the tackle.
Ospreys head physio Chris Towers said: "Tom has sustained a significant injury.
"A number of investigations need to be carried out before we can ascertain the full extent of the injury and the best course of treatment for Tom."
Better news for the Ospreys is that Ryan Jones should be ready to return to action this weekend after recovering from a leg injury.