Wales hooker Ken Owens is set to miss the autumn international programme after injuring his shoulder while playing for Scarlets against Glasgow.
Uncapped flanker Josh Macleod is also in line to miss the six-match series because of a hamstring problem suffered in the same game.
Dragons hooker Elliot Dee and Scarlets flanker James Davies have been called up to the squad as replacements.
Dee joins Ryan Elias and uncapped Sam Parry as Wayne Pivac's hooker options.
Owens and Macleod have both been released from the Wales squad because they have not been able to take a significant part in training.
No details have been revealed by the Welsh Rugby Union of the severity of the injuries or length of the time they can expect to be on the sidelines.
Owens, 33, came on as a second-half replacement in the 20-7 defeat at Scotstoun.
The Scarlets skipper left the field himself after a heavy challenge while taking a quick penalty in the final few minutes.
Macleod, 23, had been one of seven uncapped players named by Pivac in his initial 38-man party after impressing with Scarlets over the last 12 months.
Wales have a friendly away to France on 24 October followed by the rearranged final 2020 Six Nations match against Scotland on 31 October at Parc y Scarlets.
Four more games follow in the new Autumn Nations Cup.
Pivac's side will play Ireland, Georgia and England in pool matches before a final game on 5 December.
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