10 things to know for the U.S. Open

Venus Williams, left, and Serena Williams, of the United States, laugh during an exhibition doubles match at the Rogers Cup in Toronto on Monday, Aug. 5, 2013. The two tennis superstars joined celebrity chef Marcus Samuelsson for a cooking demonstration Thursday, Aug. 23, 2013 as part of the an event leading up to the U.S. Open championships in New York City. (AP / The Canadian Press, Frank Gunn)

NEW YORK -- A look at 10 of the top topics at the U.S. Open, the hard-court Grand Slam tennis tournament that begins Monday and ends Sept. 9:

1. Murray's first defence: For the first time, Andy Murray will be the defending champion at a Grand Slam tournament -- and he suspects he'll be more nervous than usual in the early rounds. Will be intriguing to see if that's true. His championship at the 2012 U.S. Open made him the first man from Britain to win a major title since Fred Perry in 1936. And last month, Murray ended Britain's 77-year wait for a male champion at Wimbledon.

2. Rafa returns: Rafael Nadal has gone through all manner of ups and downs over the past two seasons, including a seven-month absence because of knee trouble -- he missed two Grand Slam tournaments, including last year's U.S. Open -- plus two more French Open titles and two quick exits at Wimbledon. He's looked terrific lately, improving to 15-0 on hard courts in 2013 by winning the Montreal and Cincinnati tournaments this month. He's back up to No. 2 in the rankings, behind only Novak Djokovic, who has reached at least the semifinals in each of his past six visits to Flushing Meadows.

3. Federer at No. 7: Roger Federer's 17 Grand Slam titles include five at the U.S. Open. He was ranked No. 1 for more weeks than any man in history. He was seeded No. 1 at 18 consecutive Grand Slam tournaments from 2004-08. And now? Well, he turned 32 this month, has fiddled around with a bigger racket, is coming off his earliest loss at a Grand Slam tournament in a decade, and is seeded No. 7 at the U.S. Open. If he makes it to the quarterfinals, he'd face his nemesis, Nadal.

4. Anyone outside the Big 4?: The so-called Big 4 of Federer, Nadal, Djokovic and Murray have combined to win 33 of the past 34 Grand Slam titles, a stretch that began in 2005. Is there any chance anyone else breaks through at this tournament? Any discussion of other contenders must begin with the guy who kept it from being 34 of 34 -- Juan Martin del Potro, the 6-foot-6 Argentine with the booming forehand who surprised Federer in five sets in the 2009 U.S. Open final. Another big hitter to keep an eye on? No. 5 Tomas Berdych, the 2010 Wimbledon runner-up, although consistency is not his strong suit.

5. The American Men: Andy Roddick's name might very well be mentioned as much over the coming weeks as Perry's has been uttered at Wimbledon. This U.S. Open is the 40th Grand Slam tournament since an American man won a major title, Roddick's at Flushing Meadows in 2003. Used to be unthinkable that the United States would go a full decade without claiming one of tennis' most prestigious titles. Earlier this month, for the only time in the 40-year history of the ATP computer rankings, zero U.S. men appeared in the top 20. John Isner, who is listed at 6-foot-10 and can serve as well as anyone, moved back in; he's seeded 13th and could play Nadal in the fourth round.

6. Williams tries to make it two: For all Serena Williams has accomplished, one tiny thing missing from her resume is a successful title defence at the U.S. Open, the site of a couple of her infamous meltdowns. She won her fourth trophy at Flushing Meadows last year, edging No. 2 Victoria Azarenka in a gripping three-set final. When Williams is on, she's certainly the woman to beat. But Azarenka believes she has a chance against Williams, a rare quality on the women's tour; Azarenka won their final at Cincinnati this month. Still, Williams is ranked No. 1, which means she's seeded No. 1 in New York -- the last time that happened was 2002, and she won the tournament.

7. Who is not there: Maria Sharapova surprisingly withdrew the day before the draw, leaving the field without a four-time Grand Slam champion and TV broadcasters without one of the sport's top stars. Even more surprising: Wimbledon champion Marion Bartoli isn't entered in the U.S. Open, either, and it's because she suddenly announced her retirement this month at age 28. Also absent is Mardy Fish, who used to be ranked in the top 10 and was a quarterfinalist in New York two years ago, but hasn't played in a Grand Slam tournament in 2013 as he tries to come back from a heart issue.

8. Young American women: Sloane Stephens is seeded 15th, and the sport's biggest stages bring out her best tennis: She upset Williams en route to the Australian Open semifinals, made it to the Wimbledon quarterfinals before losing to eventual champion Bartoli, and got to the second week at the French Open, too. The 20-year-old Stephens is hardly the only up-and-coming young American who could draw attention. Jamie Hampton, who is seeded 23rd, also made the second week at Roland Garros. Madison Keys is worth watching, too. In all, there are 10 U.S. women in the WTA's top 100.

9. Monday, Monday: For the first time in the Open era, which began in 1968, the year's last Grand Slam tournament is scheduled to end on a Monday -- a result of the push by top players to provide a day of rest between the men's semifinals and final, instead of the U.S. Open's long-standing Saturday-Sunday finish. Each of the past five years, the U.S. Open wrapped up on Monday, but only because of rain delays. Weather-related problems should become a thing of the past in the not-too-distant future: The U.S. Tennis Association announced plans to build two retractable roofs. The aim is to have a cover for Arthur Ashe Stadium by the 2016 tournament, although it might not be ready until 2017.

10. Money, money, everywhere: Another result of lobbying by top players is an increase in prize money at Grand Slam tournaments -- the U.S. Open is raising its total payout about 35 per cent in 2013, to more than $34 million. That includes $2.6 million each to the men's and women's singles champions. A player who loses in the first round of singles will get $32,000. If either Nadal or Williams wins the title, the trophy would come with a check for $3.6 million, because each earned a possible $1 million bonus by finishing atop the standings from the U.S. Open Series, which takes into account results on the North American hard-court circuit.