Wallaby wing Digby Ioane could miss the opening Test against the British and Irish Lions after undergoing a knee operation on Wednesday.
Ioane, who was chosen in Australia's 25-man preliminary squad for next month's three-Test series, was sent home from Reds' tour of South Africa for scans.
He underwent surgery in Brisbane to clean up articular cartilage on his troublesome left knee, the Australian Rugby Union said on Twitter.
It said it was "touch and go" for the opening Test in Brisbane on June 22.
The 27-year-old is seen as a certain selection on the left wing if fit and his omission would be a major blow for the Wallabies.
His surgery follows Tatafu Polota-Nau (broken forearm) being ruled out of the Lions series, while George Smith (knee) is unlikely to recover in time and Pat McCabe (knee) is also in doubt.