Team New Zealand's first day of practice racing against Luna Rossa drew their competitor's spies to the water, with a close associate of Oracle boss Russell Coutts spotted in a boat photographing the action.
After using half of their 30 sail days primarily conducting reliability checks and system testing, Emirates Team New Zealand has ratcheted up its AC72 sailing programme in recent weeks, focusing on racing and speed.
With the Italians in Auckland over the summer testing their AC72 - an identical design to the New Zealand boat - the two teams have paired up for practice racing.
Their competitors did little to disguise their presence out on the water yesterday.
Simon Daubney, who won the America's Cup with Team New Zealand in 1995 and 2000 and who is a long-time friend of Coutts, tracked the racing closely, taking pictures from a chase boat.
Daubney is now a trimmer with Ben Ainslie Racing, but was wearing an Oracle jacket, leaving little doubt that the Cup defenders and BAR are one and the same.
Team New Zealand boss Grant Dalton said the fact Oracle had representatives keeping a close eye on the Kiwi team and Luna Rossa indicated it was nervous about their progress.
"I would be worried if I were them," Dalton said.
"Ultimately, if they have a faster boat than us, they'll win. But if all the boats are a similar speed, which is looking likely, then it will come down to which team can sail the boat better.
"So with all the practice racing we are doing, I think they will be worried."
The Kiwi team have just nine of their 30 allowable sail days remaining, and Dalton said they hoped to spend most of those doing practice racing.
"It's great to finally be racing and testing these boats in race conditions instead of being by ourselves out there," he said.
Oracle's presence in Auckland can also be taken as a sign they are watching the two teams closely to ensure they are adhering to the rules.
Team New Zealand entered into a rare partnership with Luna Rossa, selling the Italian team the design for their first AC72.
As the strict rules governing the next edition of the Cup prevent two-boat testing, the two teams are not allowed to share any performance data as part of their agreement, but may train against one another.
It is expected America's Cup defenders Oracle and Swedish team Artemis, who are also based in the San Francisco area, have a similar arrangement where they will hold practice races.
Dalton said Team New Zealand will also keep a close watch on their competitors, although at this stage there is little going on. Artemis are still in the very early stages of testing their boat, which they launched just over a week ago, while Oracle remain shore-bound after suffering catastrophic damage last month when their AC72 pitch-poled in choppy conditions on San Francisco Bay.
Oracle's wing sail was destroyed in the accident, and the team are currently building a new one at their factory in Warkworth. They hope to have it shipped to the United States by January.