Sidelined in Their Prime.(sports injuries in professional tennis)

The expected drama in 2009 is raising questions about why so many tennis players are getting injured.

Tennis in 2008 was sometimes more like a casualty ward than a sport. Australian Open winner Maria Sharapova battled a shoulder injury for much of 2008 and did not play after August. French Open champion Ana Ivanovic hurt her hand at Wimbledon and never hit her stride again. U.S. Open champion Serena Williams finished the year with an ankle injury and played sparingly all season. Strangest of all, the woman who was widely expected just 12 months ago to become world No. 1 in 2008 ended up catching up on her studies at home. Justine Henin was about to hit her peak, at 25, but the effort of getting there had exhausted her physically and mentally, and her May retirement shocked the world. The men's game was similarly afflicted, with Rafael Nadal winning Wimbledon--and then suffering a knee injury in the fall that kept him out of the Masters Cup and the Davis Cup final. Roger Federer struggled for a big part of the year with mononucleosis.

This parade of injuries and illnesses will certainly add to the drama at this year's Australian Open, which begins Jan. 19. Only the fittest players can thrive in a tournament notorious for its difficult, hot playing conditions. And since Henin's departure there has been a vacuum in women's tennis. With everyone else at the doctor's office, Jelena Jankovic became world No. 1 last year, and that ranking whizzed around like a tennis ball in a high-speed rally. Any of eight players look like they could win the women's title in Melbourne. Among the men, Federer and Nadal both still look strong, but so does Novak Djokovic, the young Serb who won in Melbourne last year, and Britain's star, Andy Murray, who defeated Federer and Nadal to win an exhibition event in Abu Dhabi earlier this month.

Yet the drama ahead will come at an enormous cost--and has already raised serious questions about why so many tennis players are struggling or getting cut down in what ought to be their prime. When I won my 18 Grand Slam singles titles between 1978 and 1987, I was the fittest woman in tennis, but the global circuit was far less developed, and there was not the demand to play every week of the year. Even then the tour was too long. After 1989, the only way I could get the physical and mental break I needed was to stop playing in the Australian Open and start the tour in February. Today's athletes can't do that. Even players way down in the world rankings can win hundreds of thousands of dollars, and with ever greater financial incentives comes ever greater pressure from agents, organizers and sponsors to keep playing all year round. Some players don't have any kind of off-season ...