Williams said that despite that, the drive is still there to compete and continue to train to be the fittest she can be.
She said it is even more exciting as she loves being fit and being at the top of her game with that drive still very much there.
"A lot of players or a lot of coaches tell me that Serena is so lucky. She doesn't train. She just shows up and wins matches. God, if I could do that, I would. Oh, I would do it. Unfortunately, that's not the case. I think the older you get, the more fit you have to get to continue competing. I'm excited about it because I love being fit."