Wales are set to be without Scarlets loose-head prop for autumn internationals against Australia, Argentina, Japan and South Africa.
Scarlets say Evans, 24, is not expected to return for them until December.
He has yet to play this season, having undergone wrist surgery since last appearing during Wales' tour to New Zealand in June.
"We're not expecting to see Rob back until December," said a Scarlets spokesperson.
Evans has been vying with Cardiff Blues veteran Gethin Jenkins since the 2015 World Cup for Wales' number one spot.
In August, Scarlets head coach Wayne Pivac said he did not expect Evans to return until "near the autumn internationals".