Good breezes led to costly mistakes in the budding America's Cup season today. Fleet leader Prada erred early, then rallied to score a shocking, last-minute win to go 7-0 in challenger trials and hand Paul Cayard's AmericaOne its first loss.

Cayard saw victory snatched away in sight of the finish when his billowing spinnaker split at the top and wafted to the water in 15 knots of wind. Prada was close behind and shot by to take the finishing gun before a crowd of about 50 spectator craft.

It was up and down, touch and go all day between the two top-rated teams, as Prada won the start and led at the first mark by 23 seconds, then lost the lead with spinnaker troubles of its own. Skipper Francesco de Angelis watched in alarm as twice his Italian crew lost control of the big white sail on the first downwind run as a shackle on a control line evidently opened unexpectedly.

The gossamer sail flew out in front of the boat, Prada slowed and Cayard came rolling up from astern to take the lead. But it was all he could do to hang on over the next 2 1/4 legs through whitecapped, sunlit seas. By the final turning mark, Prada was just 15 seconds back.

The boats took off downwind, nose to tail, bound for the finish three miles away, foam creaming from the bows. Cayard left no passing lane and his victory seemed assured until the moment, 300 yards from the finish, when the bright green spinnaker split along a seam at the head and floated downward.

The crew scampered to cut the sail free but de Angelis needed no invitation. His sleek, silver racer sped straight for the finish. Prada was a boat length ahead before AmericaOne had a new spinnaker on deck and three lengths to the good before the new sail was up and drawing. That's where it ended, with AmericaOne 17 seconds back.

Earlier on the same course, the New York Yacht Club's Young America maintained its unblemished record with an effortless, 1-minute 24-second win over the Hawaiian entry Abracadabra. Young America's skipper, former match race world champion Ed Baird, manhandled another rival at the start, forcing Abracadabra helmsman Johhn Kolius outside the starting area as the final seconds ticked down.

Kolius was forced to spin his boat 360 degrees to escape the trap, wound up starting 30 seconds late and never challenged for the lead.

Baird gets his chance to do the same to de Angelis and the Prada crew on Saturday in the second so-called "clash of the titans." After that race, only one Cup team can remain unbeaten.

Challengers had only one race apiece today. The regular slate of two-a-days was cut back to make room for 300 local sailors starting the annual Coastal Cruising Classic race from Auckland north to the Bay of Islands in the morning. Once the fleet cleared the harbor, the Cup boats went back to work. The meeting of unbeaten Prada and AmericaOne started last and the result was awaited halfway around the world. Italians who were swept by a wave of enthusiasm when their challenger Il Moro di Venezia made it to the final Cup match in 1992, only to lose to Bill Koch's America 3, are being swept up by the success of the Prada challenge as well.

"It's hard to judge here," said Laurent Esquier, the syndicate chief, "but based on the number of Italian press around and the clippings coming across my desk, there's a lot of interest."

Esquier, a Frenchman in his eighth Cup campaign, cautioned against reading too much into Prada's early success. But he said the challenger field looks to be the strongest since 1986-87, when 13 challengers descended on Western Australia and Dennis Conner's Stars & Stripes wound up capturing the Cup.

The 1992 and 1995 challenger fields in San Diego were weaker, he said, because they lacked a U.S. presence. With U.S. teams defending the Cup there, all the technology and financing that goes into U.S. efforts was on the other side of the equation.

"This time you have five U.S. groups challenging, all with adequate funding," said Esquier. "That makes the challengers stronger than ever as a group."