From the beginning of Sunday's U.S. Open women's final, there was an aura of inevitability that surrounded Serena Williams like a force field.

The serve was booming, the forehand was a laser, the backhand was a dart.

Caroline Wozniacki threw everything she had at Williams, and Williams threw it right back. It took Williams an hour and 15 minutes at Arthur Ashe Stadium to defeat good friend Wozniacki, 6-3, 6-3, and put an exclamation mark on the ending of what had been a question-mark Grand Slam season.

This was Williams' third straight U.S. Open title, her sixth overall and her 18th Grand Slam victory. Those 18 Slams tie her with Martina Navratilova and Chris Evert for fourth place all-time.

But what is particularly impressive is her longevity, even in the face of serious injuries and a pulmonary embolism that imperiled her career. At 32 (she will be 33 on Sept. 26), Williams is the second-oldest major champion. Navratilova was 33 when she won Wimbledon in 1990. Williams holds the longest span between Slam titles at 15 years, starting with her first Open victory in 1999.

"I just could never have imagined that I would be mentioned with Chris Evert and Martina Navratilova, because I was just a kid with a dream and racket living in Compton [California]," Williams said. "This never happened before."

Try as she might, and she did try mightily, Wozniacki didn't have the answers to all the questions that Williams asked. Oddly, two of the three games won in the first set were breaks of Williams' serve. Yet Wozniacki couldn't hold on to her own, as she was broken in her first three service games.

And sure enough, Wozniacki was broken to start the second set and never was ahead at any point in the match. Williams even won most of the long rallies as she pulled Wozniacki back and forth as if on a string.

Wozniacki lost the best rally of the match in the ninth game of the second set, a 26-stroke point that brought the crowd to its feet. With that, Williams went to break Wozniacki's serve for the fifth and final time for a victory that earned her the $3-million winner's check plus a $1-million bonus for winning the summer series, in which she happened to beat Wozniacki twice in three sets on the way to victories in Montreal and Cincinnati.

"I had a game plan in mind, but it was kind of difficult at the start," Wozniacki said. "I tried to push her back, but that really didn't work for me. She really just stepped in and she was playing aggressively. She was playing better than me today."

At the Open, Williams didn't lose a set in seven matches and became progressively more dominant as the rounds went by. She swatted her forehands as if the ball were a mosquito, bombed the serve and showed a determination to stay in rallies, the quality of patience that is not often attributed to her.

"I think her results and her career says it all: 18 Grand Slam titles," Wozniacki said. "You don't get that unless you're exceptional in what you do . . . I definitely think that when Serena is on her game, there's not much we can do."

Williams has a manic devotion to being the best. She said one thing Sunday, but her results say everything about her ongoing determination. "I put a lot of pressure on myself," she said. "I don't have to put pressure on myself, because like I said, I don't have to win another title. I always have my little '18' bracelet now. I'm good to go."