MELBOURNE, Australia — You cannot accuse Serena Williams of not providing fair warning.
Only a few days ago, when Williams was reminded that she always had won the Australian Open title after reaching the semifinals, Williams, in the midst of rolling through this year's draw, took in the statistic then provided the caveat.
"Nothing's guaranteed in sports," she said. "I still have to win two matches against potentially two extremely tough opponents."
Perhaps it would be helpful at this advanced stage of her career not to know so well all that could go wrong. At 34, Williams has won so many big matches and big titles, growling her way through adversity of her own and the world's making, but she also has experienced a growing number of seismic shifts in her tennis fortunes.
The latest came Saturday on a court that has long been one of her safer havens, as Angelique Kerber rose to the challenge and then some in her first Grand Slam final.
Creating sharp angles and big opportunities, absorbing Williams' tremendous pace and intensity and covering the court almost as well as her mentor Steffi Graf, the seventh-seeded Kerber stunningly upset the top-ranked Williams 6-4, 3-6, 6-4 in a tense and often riveting 2-hour, 8-minute match.
Kerber, 28, converted five of nine break points and finished with 13 unforced errors to Williams' 46. Williams, who did not record her first ace until her eighth service game, finished with seven aces and six double faults. Kerber had five aces against three doubles. Her winners-to-unforced errors differential was also better, plus-12 to Williams' plus-1.
The statistics showed what the eye could plainly see. Despite her 25 previous major final appearances, Williams was the tighter player.
"I mean, every time I walk in this room, everyone expects me to win every single match, every single day of my life," Williams said in her postmatch news conference. "As much as I would like to be a robot, I'm not."
Kerber also avoided the classic trap of overplaying. She went with the percentages instead of quick fixes; earned her points by thinking clearly; and coaxed Williams into errors instead of punching the panic button and trying to be a hero.
Above all, Kerber was able to finish off her masterwork — the toughest task in a sport with no game clock and no time limit.
"The mental part, it's really big," Kerber said. "I was able to see it also. I mean you must be relaxed, and you must really believe in yourself.
"This is actually the biggest thing I learn also in these two weeks, to go for it."
Kerber has been in the top 10 for four years, and her best result in her 32 previous majors had been the semifinals at the 2012 Wimbledon and 2011 U.S. Open. Last year she lost her first-round Australian Open match and came close to repeating it this year when she saved a match point in her win over Misaki Doi.
"I had a really crazy two weeks," Kerber said. "I mean, with the first round where I was match point down, and then with the win over (Victoria) Azarenka in the quarters. I had never beaten her. And now to play against Serena, it was really an honor to play against her in a Grand Slam final.
"I think I had less pressure than her, maybe. I had nothing to lose. … I was trying really to enjoy every second. … I had goose bumps on center court when I was playing."
It was Williams' second failed attempt to reach 22 major titles and tie Graf for the career record. She lost in the semifinals at last year's U.S. Open, in perhaps even more dispiriting fashion, as she was rolling toward the sport's first Grand Slam since 1988.
"I think I helped Steffi right now," Kerber said, smiling.
But Williams was gracious in defeat. She smiled as she accepted her silver platter from Evonne Goolagong-Cawley, a four-time Australian Open champion. She congratulated Kerber on a victory that she called deserving.
"(Kerber) played so well today," Williams said. "She had an attitude that I think a lot of people can learn from, just to always stay positive and never give up."
Someone suggested to Williams later that she looked almost as happy as Kerber during the trophy presentation. Williams smiled and said, "Really? I should get into acting."
Kerber improved her career record against Williams to 2-5. The only other player in the top 10 to have more than one victory against Williams is Maria Sharapova, who is 2-19, including 18 straight defeats.
"She's had a great month," Williams said of Kerber. "I was surprised and really happy for her. I'm like, whoa, (she'll be) No. 2. What's after 2 is 1, so I guess I better be careful."