Sir Ben Ainslie is facing one of the toughest battles of his career to keep his dream of winning the America’s Cup alive after a serious mechanical failure left his Land Rover BAR team trailing 2-0 behind Emirates Team New Zealand yesterday.

Ainslie said the crew heard a “loud crunching noise” from the wing and instantly lost power as they closed on their rivals early in the opening race of their best-of-nine semi-final in the Louis Vuitton America’s Cup Challenger Play-offs.

“It’s tough, but not just myself but other guys in the team have been in tough spots before,” Ainslie said.

“Sometimes when your back is against the wall like this and you face a challenge, it’s quite motivating. To turn it around from here would be a huge achievement. Everyone still believes that and the team is still fighting hard.”

The noise seems to have been the carbon-fibre camber arm breaking and, despite initially considering racing on, Ainslie made the sensible decision to retire, which could have saved his boat from a serious accident. The camber arm controls movement and bend in the 23.5-metre-high wing that powers the boat. If they had continued, it was likely that the wing would have collapsed on top of the boat when confronted with a crosswind.

While the team does have a spare wing, with the boat stuck on the course and unable to sail at speed back to their base, not only did BAR have to concede the first race but the second race, too — New Zealand going through the motions of crossing the start line at the same moment as the BAR boat was being lifted out of the water by a crane.

“Considering what is at stake, to lose two races like that is a tough one to take,” Ainslie said. “But we’ve had tough times in the past and overcome them.”

It seemed likely that the team would switch to use their spare wing, but Ainslie was confident that the problem could be fixed and they would test the same wing on the water this morning, along with some other upgrades that were planned for today.

With stronger winds today of about 20 knots, BAR will hope that they will be able to match New Zealand in conditions neither are used to. Despite losing an aggressive pre-start to New Zealand yesterday, they were close behind until disaster struck.

Giles Scott, the BAR tactician, had called for an early tack after the first mark to ensure a split on the course and, while New Zealand made it to the second mark first, the British team was closing fast and seemed to have a speed edge as they turned the mark. Within moments, though, BAR had lost nearly all their speed, as they fell off their foils and slowed down to about nine knots. It was clearly an equipment problem rather than an error and Ainslie was quick to retire from the race — the second successive time he had done so against New Zealand.

Luck, which seemed to be on BAR’s side when Sunday’s races were cancelled in unfavourable light winds, had suddenly deserted them.

“We felt we were in for a battle today, but it was unfortunate that there wasn’t much of a battle,” said Peter Burling, the New Zealand helmsman, who added that he was confident in his boat’s performance in today’s stronger winds.

“Everyone’s done a fair bit of sailing in stronger breeze; for ourselves, it was back home before we got to Bermuda.

“For everyone here it has been the same; it has been a while since we’ve all sailed in good breeze, but we’re really confident with our boat and our equipment, and we’re pretty excited about the next few days. It [the wind] is going to be pretty upper-limit, but these boats are built for that.”

There were signs of hope for Ainslie, though, as for the first time the Land Rover BAR boat seemed capable of matching New Zealand.

“We were positive with the speed of the boat today,” Ainslie said. “Certainly, on that first run, we held our own nicely and were set up with a nice split. We are getting the performance better every day, which is clearly what we need to do.

“We just keep marching on. There is no other option than to sort the issue out, get out there racing tomorrow and win some races. The tolerances in this game are so small. Tomorrow is another day, who knows what will happen.

“It’s like the old saying — one door closes, another one slams in your face. That’s the challenge of this sport. It’s a technical sport, you are going to have failures and we are pushing these boats to the limit.”

In the other semi-final, Artemis Racing and SoftBank Team Japan are tied at 1-1 after two races.