NEW YORK, NY, USA - It almost didn't happen for her, but then again, that's when she's the most dangerous. Serena Williams pulled off a miracle third set comeback against Victoria Azarenka in the final of the US Open, fighting herself as well as a 5-3 third set deficit to win her 15th Grand Slam title.

Everything seemed lined up for Williams in the final: 13 straight wins against Top 5 players, nine straight against Top 2 players, four straight against No.1s; and, of course, five straight wins against Azarenka. And after a routine 6-2 first set, it seemed like a foregone conclusion Williams would hold that trophy.

But not so fast.

The clean numbers Williams had in the first set - 16 winners to 11 unforced errors, a +5 differential - dissipated almost as soon as it was over, as her power game went awry in the second set with a -6 differential, nine winners to 15 unforced. That second set went the opposite way to a fired up Azarenka, 6-2.

And the World No.1 continued to ride that momentum in the third set, building that 5-3 lead and even coming within two points of victory with Williams serving at 30-all in that game. But the No.4-seeded Williams came alive just in time, just like she has been known to do - she won 10 of the next 12 points to win the next three games, then broke Azarenka one last time to win, 62 26 75.

"Oh my God. I honestly can't believe I won," Williams told Mary Carillo in the on-court trophy ceremony after the match. "I was really prepared for my runner-up speech, because she was playing so great. I'm really shocked right now."

"Serena really deserved to win. She showed how true of a champion she is, and I'm honored to stand with such a champion," Azarenka said. "At the moment it's tough but I gave it my all, and stepping off this court I will have no regrets."

Williams remains in fourth place in the Open Era for most Grand Slam titles, but she's creeping up all the time - Steffi Graf leads the list with 22, while Chris Evert and Martina Navratilova are tied with 18 each, just three more than Williams' 15. The American's career haul is made up of five Australian Opens (2003, 2005, 2007, 2009, 2010), one French Open (2002), five Wimbledons (2002, 2003, 2009, 2010, 2012) and four US Opens (1999, 2002, 2008, 2012).

"It hasn't even sunken in that I'm the winner yet. It's awesome," Williams said in her press conference. "Yeah, three decades - the '90s, 2000s, 2010s, that's kind of cool. It's exciting to have this opportunity. And 13 years is a long time between the first and the last. I was reading yesterday or this morning how Pete Sampras won in '90 and 2002 - that was a 12-year span, that was awesome.

"For me to get this 13 years later, and that I'm at No.15 now, it's so cool."

Though she didn't win the title, Azarenka still proved her No.1 status, pushing one of the all-time greats to her limits before finally succumbing. The Belarusian is now 1-1 in Grand Slam finals, having won this year's Australian Open.

"Could it have gone my way? Probably, yes. But it didn't. And it really, really hurts," Azarenka said. "Those emotions come out and you feel sad, but it's time to really realize what happened today. It was a close match, but not for me.

"It was still a great achievement. I feel proud of myself in one way, but still sad. But in a few days when I go home, I'll be more than happy with the summer. I think I'm in pretty good shoes, sitting here as a finalist of the US Open.

"Serena produced some amazing tennis today. For me she's the greatest player of all time. She took the game to the next level."