Bradley Davies will be out until the New Year after undergoing an operation on an injured knee.
The 31-year-old Ospreys lock was released from the Wales national squad this month to monitor the injury but will miss the entire autumn series.
Ospreys coach Allen Clarke says flanker Dan Lydiate is ready for a Wales return after playing 80 minutes for his region against Connacht.
“That’ll give him a great sense of confidence with Wales,” said Clarke.
“Whether he’s selected or not, he’ll be in a good place.
“He galvanises a pack with his energy and the trust you have with someone like him beside you.”