(CNN)As Serena Williams chased a historic calendar grand slam in 2015, tickets for the US Open women's finals sold out before the men's for the first time.

Although her quest to become the first player in 27 years to win four majors in the same calendar year ended at the semifinals in New York, it proved her status as not just one of the world's greatest tennis players but also one of sport's biggest attractions.
But with the world No. 1 now on maternity leave, what impact will her absence have on the sport she has dominated since winning her first major at the 1999 US Open at the age of 17?
"Exceptional athletes with rare and unique talent come along once in a decade," said WTA spokeswoman Heather Bowler. "The WTA has had over four decades, each marked by exceptional players, so we know these great and new champions will emerge, some already are, and we look forward to the future."

Rising stars and comebacks

 
Williams, whose publicist confirmed last month she was expecting a child with her fiance, Reddit co-founder Alexis Ohanian, is due to give birth in the fall.