Sep 7, 2014; New York, NY, USA; Serena Williams (USA) at the trophy presentation after recording match point against Caroline Wozniacki (DEN) in the women's singles final of the 2014 US Open tennis tournament at USTA Billie Jean King National Tennis Center. [Photo/Agencies]

NEW YORK - A couple of months before Serena Williams capped her dominant run to a third consecutive US Open championship and 18th major singles title Sunday night, she sat down with coach Patrick Mouratoglou to decipher why the season had been such a struggle by her standards.

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At the time, Williams was coming off a third-round loss at Wimbledon, which followed a second-round loss at the French Open, which followed a fourth-round loss at the Australian Open and, when Grand Slam success defines a legacy, that simply wouldn't do. The quest to match Chris Evert and Martina Navratilova at 18 was weighing on her.

"It was definitely on my shoulders," Williams could acknowledge after that burden was gone. "It was definitely like, `Oh, get there. Get there. Get there."'

She knew, of course, there was one more big event left in 2014, and a finite amount of time to turn things around before heading to Flushing Meadows. In some ways starting from scratch, Williams regrouped and stopped her mini-slump, never dropping more than three games in any set, including a 6-3, 6-3 victory over close friend Caroline Wozniacki in Sunday's final.

"When Serena is on her game," said the 10th-seeded Wozniacki, who admitted she was nervous in her second Grand Slam title match, "there's not much we can do."

Williams matched Evert's total of six US Opens and became the first woman to win three in a row since Evert's four-title run from 1975-78.

Add in Williams' five titles apiece at Wimbledon and the Australian Open, plus two at the French Open, and only three players have more Slams: Margaret Court with 24, Steffi Graf with 22, and Helen Wills Moody with 19.

Ranked and seeded No. 1, Williams let Wozniacki keep things competitive for about five games but wound up compiling a hard-to-believe 29-4 edge in winners. Until a cross-court backhand in the final game, the only winners registered by Wozniacki came on aces.

When it was over, Williams dropped to her back behind the baseline, covering her hands with her face. Her first major trophy also came in New York, in 1999, when she was 17.

This time, Williams earned $4 million, a record in tennis $3 million for the title, plus a $1 million bonus for having had the best results during the North American summer hard-court circuit.

A few weeks shy of her 33rd birthday, making the American the oldest major champion since Navratilova was 33 at Wimbledon in 1990, Williams powered this way and that in her black-and-pink hightops. Wozniacki is the one training for the New York City Marathon, but she was tuckered out by the end.

Wozniacki may as well have been an extra in this Williams highlight reel. Points were directed by Williams, via serves that reached 120 mph (194 kph), forceful returns that backed Wozniacki into a corner when not producing outright winners, unreachable groundstrokes or the occasional volley.

"From a different planet," said Wozniacki's father, Piotr, who also coaches her. "Come on, there's no chance."

Yes, this was all about Williams. At times, it felt as if Wozniacki were there because, well, someone needed to be on the opposite side of the net.

They've been pals for years, and they hung out together in Miami heading to the beach, watching an NBA playoff game _ after both lost early at the French Open in May. Wozniacki says Williams helped her get over the end of her engagement to golf star Rory McIlroy. Williams said she planned to invite Wozniacki along for Sunday night's championship celebration.

"We're both going to do anything possible to win the match," said Wozniacki, a 24-year-old from Denmark who reached No. 1 in the rankings in 2010, a year after losing to Kim Clijsters in the US Open final. "After the match, we're friends again."

Mouratoglou noted the obvious: It didn't matter one bit to Williams who she was facing.

"Yeah, they're friends," the coach said, "but on the other side, believe me, Serena has zero friends."

The last time she was at a major, Williams followed her early Wimbledon singles exit with an odd episode in doubles, appearing disoriented and quitting after three games because of what she called a "bug."

"After Wimbledon, I was just so disappointed," Williams said. "I also realized I just needed to relax a little more. I put a lot of pressure on myself. I don't have to put pressure on myself."

When she met with Mouratoglou after Wimbledon to discuss how to proceed, he recalled Sunday, "She coached me. She told me, `Look, you are a guy who likes challenges. I am so low. You should be motivated by that."'

Since that chat in Paris, Williams has won 19 of 20 matches and three titles.

Only one number mattered to her Sunday night, though: 18.