Serena Williams says 'countdown' to retirement has started

Serena Williams, a 23-time Grand Slam champion and iconic tennis superstar for a generation, said Tuesday that "the countdown has begun" to her retirement from the sport.

The 40-year-old American wrote a cover essay for Vogue magazine and an Instagram post in which she set the stage for "evolving away from tennis."

"There comes a time in life when we have to decide to move in a different direction," she said on Instagram. "That time is always hard when you love something so much. My goodness do I enjoy tennis.

"But now, the countdown has begun. I have to focus on being a mom, my spiritual goals and finally discovering a different, but just (as) exciting Serena. I'm gonna relish these next few weeks."

After suffering a torn right hamstring at Wimbledon last year, Williams was sidelined until playing doubles at Eastbourne in June and made a return at Wimbledon as a wild card, losing in the first round.

On Monday, Williams competed in her first hardcourt match in 18 months, defeating Spain's Nuria Parrizas Diaz to reach the second round of the WTA hardcourt event in Toronto, a tuneup for the US Open.