Jimmy Spithill has denied boatspeed was the kingmaker on day one of the 35th America's Cup match in Bermuda.

Spithill and Oracle Team USA's quest for a three-peat got off to a shaky start today, as they suffered two heavy defeats to Emirates Team New Zealand.

The Kiwi team appeared to have a handy speed advantage over Oracle in the light conditions on the Great Sound as they streaked to two wire-to-wire wins.

But Spithill believes light, puffy conditions made it tricky to get a read on the relative strengths of each boat.

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"This breeze is pretty difficult to draw too much from boatspeed. As you saw the breeze was up and down, it was a real minefield out there. It's a pretty tough direction to be drawing conclusions on boatspeed," he said.

"There's a lot we can take from today, a lot to be learned. Clearly we weren't sailing at our best, but we also had our opportunities. Both races there were some chances. [Team New Zealand] at the end of the day made fewer mistakes.

"The good news is, we're only one back," Spithill added, referring to the quirk in the scoring system that saw Team NZ go into the Cup match at -1. Oracle earned a one-point head start in the first-to-seven series after taking out the round-robin phase of the qualifying series, but this was applied as negative point against Team NZ to ensure the series would last at least four race days.

Much has been made about the performance of Team NZ boat in light conditions throughout the build-up to the America's Cup and early stages of the regatta. The Kiwi team appear to be able to foil more stably through their manoeuvres than their opponents through the lower wind range.

With winds forecast at around 8-11 knots heading into today's racing, many believed the conditions would favour Team NZ, who took a calculated risk to pitch their boat more towards the light winds that are prevalent in Bermuda at this time of year.

Tellingly, Team NZ helmsman Peter Burling said he was comfortable with the team's boatspeed today.

"It felt like our boat was going really fast, which is really pleasing," said Burling.

The forecast for races three and four tomorrow is shaping up to be similar to today, with an easterly of around 9-11 knots predicted.