Buzzing on Yahoo Sports:

Challenges at the top

Martin Rogers
Yahoo Sports

The longest season in sports begins this week, as the tennis world commences its grueling, 11-month, inter-continental slog in search of prize money, ranking points and Grand Slam glory.

The new year has a lot to live up to. After all, 2008 gave us no less than the greatest match ever played as Rafael Nadal and Roger Federer traded blows across Wimbledon's historic lawn.

There was the retirement of a phenomenon, with tiny Justine Henin calling time on her glittering career in order to seek a level of personal happiness to match her professional success.

As we look ahead to 2009 there is plenty of uncertainty, but also much anticipation. With a restructuring of the men's tour and exciting rivalries at the top of both the men's and women's game, tennis fans should have a steady supply of intrigue to tide them through the year.

Here are the big questions and story lines that mark the start of the new season:

1. Will Nadal's body hold up?

It always was going to take something spectacular to topple living legend Roger Federer from the No. 1 spot that he had come to regard as his personal property.

Rafael Nadal provided it in 2008, compiling an extraordinary season that sealed the young Spaniard an eternal place in history and lit up one of world sport's great rivalries. Nadal became the first man since Bjorn Borg in 1980 to win the French Open and Wimbledon in the same year, then went on to win an Olympic gold medal.

However, by the end of the year his body once again was in pieces, forcing him to miss the Davis Cup final and raising fresh concerns about his health.

The 22-year-old's ferocious style of play places a huge strain on his body, but two things may save him: a bigger first serve and a new ground game that involves him stepping further into the court to hit winners instead of just wearing opponents down from behind the baseline. Both measures, masterminded by coach and uncle Toni Nadal and embraced by the player, should shorten the amount of time he has to spend on court.

2. How will the ATP's new order affect men's tennis?

The new year brings a dramatic revamp of the men's tour and ranking system. There now are four tiers, with the four Grand Slams yielding the most points (2,000 for a win), followed by eight Masters tournaments (1,000 for a win), 11 third-tier weeks worth 500 ranking points and 39 or 40 bottom rung “250” events.

In an attempt to increase player participation in key tournaments, stars who skip any of the eight Masters events without a valid reason face suspension and a loss of bonus money. This could cause friction between players and the Tour, and bring the matter of what is a legitimate injury and what isn't into sharp focus.

3. Who will step up to fill Henin's shoes?

Justine Henin's sudden retirement last year opened up the top of the women's game, and no one has stepped forward as a clear dominant force.

Jelena Jankovic ended the year at No. 1, but there has been little performance difference among the top six. No. 9 Maria Sharapova should play a much heavier 2009 schedule after returning from injury while 12th-ranked Caroline Wozniacki is a fast-emerging 18-year-old with a big game and model looks.

Venus and Serena Williams may not play enough tournaments to claim the top spot, while Dinara Safina, Elena Dementieva and Ana Ivanovic all have designs on establishing themselves as queen of the court.

4. Will the Big Three become a Big Four?

Roger Federer's dip – by his own ludicrously high standards – allowed Novak Djokovic to emerge as a force in 2008. Djokovic begins the new season just a handful of points behind Federer at No. 3 as he prepares to defend his Australian Open crown.

But there is another man who looks poised to breathe down the necks of Nadal, Federer and Djokovic: 21-year-old Scot Andy Murray.

Murray enjoyed a superb run late last year, winning two Masters Series titles and reaching the U.S. Open final while displaying newfound fitness levels built by an intense program under the guidance of two full-time physical trainers.

The reason he appears to be the only player capable of breaking the Big Three's monopoly is that he is not scared of them, having beaten Federer four times out of six and toppling a tired Nadal in the semifinals at Flushing Meadows.

Murray has the chance to pick up a mountain of points at the Aussie Open later this month, having lost in the first round there last year.

5. How motivated are the Williams sisters?

Venus and Serena clearly are the most accomplished players in the world. However, with a swath of off-court interests ranging from business to fashion design, tennis is far from being the sole priority in their lives.

Don't expect the sisters to sweep through the Grand Slams – indeed, Venus has not won a major other than Wimbledon since 2001. She again will be a heavy favorite on the London grass in the summer, while Serena will be hungrily eyeing the Australian Open and U.S. Open titles.

But how much longer can they play at a high level? When his girls were still in their teens, Richard Williams said he wouldn't be surprised if they retired by their mid-20s. Venus now is 28 and Serena 27, so there might not be much more left from them.

Sign up for Yahoo Fantasy Football