Video: Serena Williams shines in new Gatorade commercial

Former World No.1 Serena Williams graced a new Gatorade ad which put emphasis on inner belief.

The 40-year-old 23-time Grand Slam champion also said "What's inside me is inside you too" in the highly motivational near-one-minute video she posted on her Instagram account.

Williams, who is just one Major title shy of Margaret Court's record, made a comeback to the Grand Slam stage at Wimbledon this year. She went on a near one-year break due to injury before returning to competitive action in doubles in Eastbourne prior to playing in London.

In the ad, Williams is initially seen holding a racket and then tossing a ball as she is donned in a tennis outfit. The commercial was part-animation, and the words "belief," "determination" and "resilience" were given emphasis.

Williams was speaking through a voice-over, with an animated tennis player hitting serves and a backhand shown in-between. The animation was then zoomed out to show a young tennis player at the end of the video.

"What's inside me is inside you too. Belief is my inner strong. I think it's the most important thing. I have to rely on myself. Determination keeps me going again and trying and trying and trying.

"I think there's a moment when everyone's inner strength wavers. There's no one else I can rely on. I'm out there by myself. If you're prepared, you're going to be confident in those moments. Being prepared for my next challenge. Belief is my inner strong. What's inside me is inside you too," said Williams.