NEW YORK -- Serena Williams is already one of the planet's most talented tennis players. She's won a U.S. Open title, been ranked in the top 10 for three years and graces the current cover of Time Magazine. And she's still only 19 years old.

	The U.S. Open is only Serena Williams' ninth tournament of the year.

Now, Williams insists, she's actually going to get serious.

"I'm definitely going to play a bit more next year, maybe in the earlier part of the year, to make sure I can do well at the Australian Open this year," Williams said on Wednesday. "Maybe I'll play more clay court events because I haven't had any clay court warm-ups before I played the French Open. I definitely am going to try to do better at those two Slams in particular."

Apparently, exiting in the quarterfinals of Grand Slam events -- something that has happened at the Australian Open, French Open and Wimbledon this year -- is no longer acceptable. There has been a vague suspicion in tennis circles that Williams, despite her glorious resumé, has been a terminal underachiever.

Certainly, she plays less than most of her talented peers. A knee injury cost her 2½ months last year and she finished only 37-8. This year's U.S. Open is only Williams' ninth tournament -- by comparison, older sister Venus is playing in her 13th event and No. 1-ranked Martina Hingis is in her 17th. Serena is 31-6, including her first two matches at the National Tennis Center. That's a total of 68-14 in two years. Hingis is 52-12 this year alone and 129-22 over the past two seasons.

	“	I think the next level for me is top three and then top place. Obviously, I haven't been able to reach that because I'm not playing the tournaments I need to play. ”
		— Serena Williams

Both Serena and Venus were brought up outside the conventional junior tennis circuit. Their father and coach, Richard Williams, has always stressed independence and outside interests. In their early professional years, the sisters played fewer matches than the norm, particularly the run-up tournaments before the Grand Slams, which are critical in making the transition from hard courts to clay, clay to grass and grass back to hard courts. Something that exacerbates the situation is the fact the two sisters do not like to play in the same tournaments; they generally meet only in the four Slams, plus Indian Wells and the Ericsson Open.

When Serena won the U.S. Open in 1999, it was the first Grand Slam singles title for the Williams sisters and it was widely believed that Serena would ultimately win more Slams than Venus. Now that Venus has won three major titles (three of the past five), there is a perception that Serena's tenacity will carry her farther.

Serena, it seems, has concentration issues.

"I'm doing better mentally," she said, suggesting that previously she was doing worse. "I watch [tapes of] matches where I haven't played well and learn. I need to get focused more. When I do, I do better."

When she was asked last month by a California reporter why she wasn't more focused, she shrugged.

"I don't know," she said.

In the locker room and in between the lines of their comments to the press, Williams' peers have little use for her gamesmanship. By Serena's own count, she has suffered food poisoning three times this season, most notably at Wimbledon. A number of players, including Jennifer Capriati, who defeated her there in the quarterfinals, wondered if it was really food poisoning. To this day, Serena maintains it was.

"I'm really picky now about the food that I eat because I have a sensitive stomach," she said. "I make sure if I go to a restaurant, it's a classy restaurant."

That would be Benihana, the Japanese grill. "If I could go there every day, I would," Williams said.

	Venus Williams, left, and sister Serena try to avoid situations where they are competing for the same trophy.

There also have been bouts with fatigue, the flu and her cranky knees. One of the prices Williams pays for inactivity is a shorter shelf-life in tournaments. When she was ranked No. 4 in 1999, she didn't see the best players until the semifinals of big events. This year, she's run into Capriati twice in Slam quarterfinals and Hingis in the other.

Williams has won twice this year, when she defeated Kim Clijsters at Indian Wells and two weeks ago in Toronto when she muscled Capriati in three sets.

Williams remains one of the favorites here because she understands what it takes to win here and has the big game to accomplish it. After losing her first set to Anca Barna, Williams has been superb. She's dropped only five games in four sets, but that will soon change.

Because she is seeded No. 10, Williams would face No. 6 seed Justine Henin, a tough customer, in the Round of 16. The next two matches, if form prevails, would be No. 3 Lindsay Davenport in the quarters and No. 1 Hingis in the semifinals. Sister Venus or Capriati could be waiting in the final.

"I think the next level for me is top three and then top place," Serena said. "Obviously, I haven't been able to reach that because I'm not playing the tournaments I need to play. If you see with my results, if I played more I definitely would be a better-ranked individual than I am right now."

Maybe it's that simple.

"I've always been serious about my game," she said. "But I think now maybe I'm a little more serious, I guess, if you want to put it that way. I'm just really geared up to move up to the next level. I've been on the same level for too long now.

"It's time to move on, let it go."

Greg Garber is a senior writer for ESPN.com.