Team NZ lead Oracle 6-0 in the first-to-nine series, with the Cup holders, winners in race four, still needing to win another race before they can start scoring points as part of penalties imposed by the international jury.
"We've still got three more races to win and although that doesn't seem like a lot, it is a lot of hard work to get there," said Barker.
His opposite Jimmy Spithill also isn't ready to call it a match, promising his team will continue fighting to the very end. He said despite Team NZ's obvious speed advantage, he still believes Oracle can win races.
"In my mind it's a long way from over," said Spithill.
The Oracle skipper also explained his decision to dump Kostecki from the boat, saying it was a case of needing to try something new.
"It was really a matter shaking things up - it's sort of professional sport these days, if you've got a lot of depth on the bench sometimes you'll try something to shake things up. In Ben and JK we've got two of the best guys in the world and we're fortunate we can rotate like that," he said.
Ainslie had a tough introduction to the America's Cup, with Team NZ out-witting the defenders with a masterful tactical performance upwind in the first race of the day.
Instead of relying on their upwind power as they have in previous races, it was clever tactics that paid off for them on the beat today. Team NZ cruelly exploited Oracle's weakness in their manoeuvring, forcing Jimmy Spithill into a tacking duel upwind, with the Kiwi boat gaining a boat length in every tack. The duel was set-up by an aggressive play at the second cross as Team New Zealand, with the starboard advantage, pulled a dial down on Oracle, forcing them to dip lower to avoid the Kiwis.
From that point on Team NZ had control of the race, wearing the Oracle crew down with their relentless tacking.
But Barker was once again disappointed with their start, after he miscued his move in the start box and handed Spithill a seven second lead at the first mark.
The Team NZ skipper later fessed up and explained he had made a rookie error in the startbox.
"Right from the entry the timing was a bit out and I was actually looking at the wrong number in the pre-start and we put ourselves in a bad position and from there we basically conceded the start so I was pretty pissed off with myself," said Barker.
The crew quickly made up for Barker's error, immediately getting themselves back into the contest with two slick foiling gybes down the first run to put them in a good position to make their move on the upwind leg.
Barker was much happier with his effort in race seven, as the Kiwi boat charged out of the blocks to run over the top of Oracle who has positioned themselves at the leeward end of the line.
From there it was relatively straight forward for Team New Zealand as they completed a wire-to-wire win.
