Geitz will miss the remainder of the Real Insurance Netball Test Series, which resumes on Sunday against England in Bendigo, after injuring her knee in the second quarter of the final Constellation Cup Test in Auckland.
The 26-year-old will immediately return to Brisbane to undergo further examination and begin treatment to limit disruption to her ANZ Championship pre-season.
"It's never an easy decision to make, particularly when it involves your captain, however, in consultation with our medical staff, we've opted to err on the side of caution," said Diamonds coach Lisa Alexander.
"We've taken a conservative approach to managing her injury to ensure a full recovery ahead of next year's ANZ Championship."
The Diamonds secured a historic clean sweep over the Silver Ferns for the first time since the Constellation Cup's inception in 2010 with a four-goal victory over the Silver Ferns in Auckland.
The victory extended the Diamonds international winning streak to 17 games and nine consecutive over New Zealand - eclipsing the second longest winning streak against the Silver Ferns in history - one game shy of equalling the record.
Captain Geitz said it was a disappointing way to finish a memorable year after leading Australia to the Commonwealth Games gold medal and Constellation Cup title.
"Missing the England series means that I can be back ready for the ANZ Championship so it's nothing too serious, rather just an opportunity to make sure I get it in tip top shape for the big year ahead," Geitz said.
"I obviously would have loved to stay on for the remaining two Tests but I've got no doubt that the players are capable of getting the job done against England before a well deserved break."
Defender Rebecca Bulley has been recalled into the team for the two-Test series and will join the team this evening.
The Australian Diamonds travel to the central Victorian city of Bendigo on Thursday ahead of the first outing against England since the thrilling one-goal victory at the Glasgow 2014 Commonwealth Games.
Australia and England will renew their international rivalry with the first Test at a sold out Bendigo Stadium on Sunday. Catch all the action live on FOX SPORTS and SBS 2.