Serena Williams trolls BFF Kim Kardashian over tennis technique

What's a little teasing between friends? After seeing Kim Kardashian's latest Instagram post, Serena Williams is offering her celebrity BFF some tennis lessons.

Kardashian posted some sultry snapshots from a tropical tennis court on Saturday, clad in a pink bikini and matching cover-up, but one crucial detail of the photoshoot showed that this Barbie doesn't play tennis all that often. Her grip on her tennis racquet prop—flat, and trailing behind her—was a dead giveaway for Williams and others, and the 23-time Grand Slam singles champion wasn't above teasing her pal amongst thousands of comments.

“Literally not how you hold a racquet. Clearly I have to give you lessons lol," Williams wrote, adding heart-eye emojis.

Kardashian and Williams have been close friends for years, with both attending each other's respective weddings. The pair are frequently pictured together at high-profile celebrity events, and in July, they attended Lionel Messi's Inter Miami CF debut.

But the socialite might need to wait her turn, because "Coach Mama" has another pupil she's training first: her first-born daughter.

Also this week, Williams' husband, Alexis Ohanian, shared a photo of Alexis Olympia Ohanian, Jr. hitting on a tennis court. Williams has been open about the love that Olympia, now 6 years old, has for tennis, and has routinely posted photos and videos on social media of the two on the tennis court together.

And when former doubles world No. 1 and current coach Rennae Stubbs weighed in on X, formerly known as Twitter, that she's "available" to take on a new charge, Ohanian made sure to let the world know that Olympia's already in world-class hands.

"Duly noted," he wrote in a reply. "I'll mention to Coach Mama."

At the rate things are going, she might have to start charging by the hour.