Joseph-Aukuso Suaalii requires surgery on a fractured jaw, placing him in doubt for the Wallabies' blockbuster British and Irish Lions duel.
The code-hopping NSW Waratahs star copped an accidental knee from a teammate in Friday's loss to the Queensland Reds and was carted from Allianz Stadium in a medicab.
The 21-year-old was concussed, but there was optimism he would miss just one week as the Waratahs pushed for a Super Rugby Pacific finals spot.
But on Wednesday the Waratahs revealed their star NRL convert required surgery to reinforce a fractured jaw.
A review in four weeks - about one month before the three-Test series begins in Brisbane on July 19 - will determine his return-to-play time frame.
There are three Super Rugby regular-season games remaining before a three-week finals series. The Wallabies begin their Test season against Fiji in Newcastle on July 6.
"We will do all we can to facilitate his recovery in consultation with Rugby Australia to have him in the best shape possible for his availability for the Wallabies," Waratahs coach Dan McKellar said.
Suaalii made a statement in his Test debut last year before he'd even played a game for the Waratahs, and has since flourished playing both at fullback and in the centres.
Speaking on Monday, Wallabies coach Joe Schmidt said he'd prefer not to wrap Suaalii in cotton wool.
"I'm keen to see him keep playing," he said.
"He's missed a few games already this season. He hasn't had that many games anyway so, for Joseph, it's important that he just keep playing when he's fit and available to play."
The setback adds to a pile of injury concerns, with flyhalf contenders Tom Lynagh (concussion) and Noah Lolesio (back) both key omissions for the Reds and ACT Brumbies, who play each other on Saturday.
The Reds are also carrying Test skipper Harry Wilson (arm) and contenders Matt Faessler, Josh Flook, Lukhan Salakaia-Loto, Liam Wright and Seru Uru on their injury list.
Waratahs flyer Max Jorgensen (ankle), in-form Western Force back-rower Carlo Tizzano (pectoral) and winger Dylan Pietsch (quad) are also nursing wounds.
