From the same Tennis article I referenced before:
To compel the game's top talent to play the most important events, the tour has adjusted the ranking system so its Premier-level tournaments are weighted more heavily. And if the players miss the top events, they will no longer be allowed to substitute points earned at smaller tournaments; instead a zero will be factored into their ranking. The tour can also suspend players if they skip and tournament and don't agree to help promote the event.
The WTA hopes the schedule will reduce injuries and improve business, as guaranteeing more stars at larger events will attract more fans and bring in more money. Yet Groeneveld and others worr that the best women will ahve to play additional tournaments to maintain their rankings. "With the season shortening, they're putting a lot more pressure on [the top players] physically and mentally," Groeneveld says.
Serena Williams agrees. "I don't think the new schedule limits anything, really," she says. "The season ends sooner, but you play more faster."
Larry Scott, the tour's CEO, says players who commit to the most important events and do well at them will find that the new season helps them in the long run. "If players wind up feeling burnt out or playing to much, it will be because they chose to play extra events," he says. "It won't be because the system forces it, that's for sure."
Jelena Jankovic, who played 97 singles matches in 2007, without, she says, so much as breaking a nail, doesn't worry too much about the schedule. "It's the way you prepare and the way your body is," she says. "You can't expect taht just because you play less tournaments you are going to be healthy."