Highly-rated Australian forward Simon Kennewell has suffered a cruel injury blow on the eve of the Sydney 7s that will also keep him out of this year's Commonwealth Games and World Cup.
The 21-year-old ruptured his anterior cruciate ligament at training on Tuesday and will undergo surgery, ruling him out of the rest of the season's World Series.
Kennewell was earmarked by USA coach Mike Friday as one to watch ahead of the teams' Australia Day battle on Friday.
Instead he will be on the sidelines, replaced by World Series debutante Tom Connor.
No stranger to injury after a horror achilles tear two years ago, captain Lewis Holland said the squad would be out to win it for him this weekend.
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"Simmo was very unlucky; he played well at the start of the season the preseason and is a valued team member we'll dearly miss," he said.
"Hopefully we'll put on a good performance for him this weekend."
It is a further blow to the side after the shock retirement of former captain Ed Jenkins last week as they hunt their first World Series title since 2012.
"He's been one of our most improved players in the last year and is now a player that the opposition fear and respect," coach Andy Friend said
"It's a cruel blow for him personally but also us as a team with so much at stake for us over the next six months.
"Simon is a fighter though, and with the full support of the squad, we know he'll come back bigger and better."
Australia begin their Sydney 7s campaign against the USA before further pool games against Scotland and Canada ahead of Sunday's final.
The hosts are sixth after two World Series events this season but have their sights firmly set on winning on home soil.
"In our own backyard we're looking to get the cake," Holland said.
"We're going out here with no less than first place (in mind) and hopefully we'll achieve that this weekend."
