Key Biscayne, Fla. ? Hot weather, a formidable foe, rowdy fans and the law of averages failed to faze Serena Williams.

Still unbeaten in 2003, the top-seeded Williams rallied past Jennifer Capriati for the seventh consecutive time Saturday, 4-6, 6-4, 6-1, to win the Nasdaq-100 Open.

Playing on her 27th birthday didn’t help Capriati, the runner-up for the third year in a row. She also lost to Serena last year and to Venus Williams in 2001.

Andre Agassi, bidding for his sixth Key Biscayne title and his third straight, will play No. 5 Carlos Moya in the men’s final today. Agassi, seeded second, advanced by beating No. 9 Albert Costa 6-2, 6-4.

The No. 6-seeded Capriati started fast but acknowledged that the 85-degree heat — and Williams’ relentless groundstrokes — took a toll in their two-hour slugfest. By the final game, Capriati was hitting so wildly that Williams had to duck out of the way of one shot.

“It was pretty hot out there,” Capriati said. “It’s tough chasing down her balls.”

Said Williams: “I saw she was getting tired. And I was just starting.”

Both players consider Key Biscayne their home tournament. But while Williams wore Florida orange, the noisy stadium crowd was firmly in Capriati’s corner — and disruptive during at least a couple of points.

“If anything, it motivates me to want to win,” Williams said. “I can understand — it’s her third time in the final. Honestly, if she was playing anyone else, I would have liked to see her win.”