The top-ranked tennis player wasn't able to make it to Wimbledon this year, but don't worry, she's keeping plenty busy with drill practice.
Williams posted a video of herself putting in work on Monday morning, as her sister Venus, 37, held down the fort in London.
"Wimbledon got me like: Easy standing drills this morning. Go easy," Williams captioned a video of herself effortlessly flicking a ball around. (Well, she makes it look effortless, anyway. We're sure it's harder than it looks!)
A second photo shows Williams cradling her bump with one hand, racket in the other.
The caption reads, "Sorry, White. Average Joes for life! And that goes for both of us." It's a response to a tweet from actor Ben Stiller last week, in which Stiller, 51, challenged Williams in costume as "Dodgeball" character White Goodman. It appears Williams will participate in a charity game for The Stiller Foundation, which provides educational opportunities for children around the world.
"Hey Serena! Now that you're the first woman to win a Grand Slam title while pregnant, let me impregnate you ... with this thought," Stiller said in a video. "It's time we co-mingle our forces. You dominate the tennis world, I dominate the dodgeball world. Globo Gym or Average Joes? Pick a side!"
It looks like Williams has chosen. (And so has her unborn doubles partner).
Now that's one heck of a backhand! But hey, it's for a good cause.