Sydney FC defender Allie Greene has issued a warning to rival A-League women's sides hoping to get an easy ride with Sky Blues' Courtney Wines and Remy Simson on international duty.
Vine and Siemsen were called up to Matildas' Asian Cup squad last week after leading the Sky Blues line in disastrous fashion to start the season.
Both have scored four goals each and while Siemsen is locked in the 23-player squad, Vine will have to fight it out for one of the two remaining places.
Sydney will face Canberra without both players for the first time this season at the Cogarah Oval on Saturday and Greene said the onus is on others to move forward in his absence.
"It's a very important time of the season, but we've put ourselves in good shape," Green told the AAP.
"It is mid-season now and we are looking to score.
"Obviously a lot has come through Kourtney and Remy who are now away from the national team.
"They are unstoppable at times, but we have options sitting on our benches who can start for most teams.
"She's been Maria Rojas and someone like her would be very excited to be on the team.
"She can provide a different form of attack and she can be overly dangerous."
While Sydney's goal-scoring has been exemplary, the work behind them has remained largely unheard of.
The Sky Blues are undefeated to start the season under the guidance of Ante Zurich and the only goal they conceded was in their first-round win over Newcastle.
Green has been integral to that success and while she herself may be considered unlucky to miss out on Matilda's berth, the 23-year-old is hoping to keep Sydney's defense of stone intact.
"Our defense has been really strong. It's something we're very proud of," she said.
"I think we can be a little more clinical with our demise.
"Whoever has been in our backline has worked for and for us. As a team we really want to keep that going."