Rhys Webb suffered ankle ligament damage as his side were trounced 32-8 by the Wallabies and will undergo surgery on Friday.
The Welsh Rugby Union (WRU) confirmed the 27-year-old faces at least 12 weeks of rehabilitation, jeopardising his participation in the Six Nations, which begins on February 4.
“Scrum-half Rhys Webb has been released from the Wales squad due to an ankle injury,” read a WRU statement.
“Webb suffered ankle ligament damage in the fixture against Australia and will undergo surgery tomorrow [Friday].
“It is expected that Webb will undertake a period of rehabilitation of at least 12 weeks.”