While Venus Williams gears up for her tennis resurgence, Serena Williams has been savoring retirement. Yet the 23-time Grand Slam winner has hinted at a comeback, and one of her past coaches suspects she might be hitting the courts again soon.

After a hiatus of 16 months, Venus triumphantly returned to the sport in Washington, though she bowed out in the second round of both singles and doubles. She’s continued to compete, including in Cincinnati, and is set to play in the U.S. Open mixed doubles.

At 45, Venus is a shoo-in for a main draw singles wildcard should she choose to accept it. Coach Rick Macci, who played a pivotal role in the early careers of the Williams sisters starting in 1991, anticipates a possible reunion with Serena in the women’s doubles at the U.S. Open.

Macci, a Hall of Famer with the United States Professional Tennis Association, has kept an eye on the buzz surrounding a Serena Williams comeback. He feels that the ex-world No. 1 might join forces with Venus at Flushing Meadows later this month.

“Asked if Serena will play doubles with Vee at the OPEN. My gut is probably because at the end of the day, Serena can still play even though she has been away,” Macci shared on Twitter. “Her serve is still one of the best on the planet and when she competes her mindset is like granite.”

The younger Williams sister has been stirring up excitement with enigmatic posts on social media, hitting the practice courts and putting in work at the gym.

Last month, the 43-year-old tennis icon posted a video of herself practicing rallies, captioning it with a reminder to her followers that she’s “Still Serena.” She also shared a snapshot of herself playing tennis while cradling her youngest daughter, Olympia, in her arms.

As Venus made her return to the court in Washington last month, the sisters practiced together once more. Venus expressed that tour life would be “better” with Serena still in the game, but she remained uncertain about any comeback plans her sister might have.

“I don’t ask those questions. I don’t ask her that. I’m her biggest fan. I never wanted her to retire,” Venus, a seven-time Grand Slam champion, remarked.

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“I don’t know what she’s going to do. I don’t ask those questions. I think we always hit the ball, because that’s who we are, we’re always hitting.

“Quite frankly, it’s great cardio. You get great legs and great arms from tennis, quiet as it’s kept. So obviously that’s part of her goal too is to stay in shape.

“I mean, I keep saying to my team, ‘The only thing that would make this better is if she was here’, like we always did everything together, so of course I miss her. But if she comes back, I’m sure she’ll let y’all know.”