Wallabies scrumhalf Jake Gordon faces missing the test season after going down with a suspected Achilles tendon injury in the Waratahs' final Super Rugby game of the year.
The 32-year-old took a quick tap late in the first half during their 31-25 loss to Western Force in Perth on Saturday evening before his right leg gave way.
"It's a question mark around an Achilles there, so shattered for Jake," said Waratahs coach Dan McKellar.
"No one cares about New South Wales and the Waratahs more than Jake, and just for him to do it in the last game of the season before the test season is about to begin, it's disappointing.
"He's certainly a loss. He has so many qualities to his game."
The Wallabies start their year against Ireland in Sydney on July 4 to kick off the inaugural Nations Championship before meeting France a week later in Brisbane, then Italy in Perth.
Gordon's recently retired Wallabies teammate and fellow scrumhalf Nic White was commentating on the match and said he spoke to Gordon at halftime.
"Unfortunately, it sounds like he's done his Achilles," White told broadcaster Stan Sport.
"Said it felt like a weird sensation down there as soon as he took off. He's pretty gutted."
Gordon has been Australia coach Joe Schmidt's preferred starter at No 9.
Should he be ruled out, Tate McDermott and Ryan Lonergan top the list as his replacement now that White has hung up his boots.
Victory meant the Western Force leapfrogged the Waratahs to finish the season in seventh, with both sides missing out on the playoffs.