After her successful run at the WTA Finals in Singapore, World's no.1 Serena Williams is now shifting her attention on several endorsement deals, one of them is a bra commercial with Berlei.

Earlier this year, Serena and Berlei already did a project together in a smoking hot advertisement. Now, the 33-year old Williams confirmed on Wednesday via Twitter that she's currently doing another commercial with the Bra company.

"On the set shooting a new Berlei bra commercial. I'm really starting to regret eating those peanut butter cookies & all that candy yesterday," Williams posted on her Twitter account.

Williams posted a photo afterwards on her Instagram account, giving her fans a glimpse of what she will look like in the upcoming television commercial with Berlei.

Despite dealing with injuries and emotional problems, It has been a triumphant year for Williams, who retained the no.1 spot in the WTA World rankings and captured both the US Open Championship and the WTA Finals in Singapore last week.

"It was really up and down. I'm glad I came and I was able to end well. So I think that was important. It's not how you start; it's how you finish, right?," Williams said in an interview via the New York Times.

"I never really talk about my goals. Thank God because if I mentioned them last year, I would've been sorely disappointed with my year this year," the world's no.1 added.

Williams recently passed former rival Martina Hingis for fourth place in the list of longest reigning world's no.1 in the history of WTA Tour. She's now just trailing women's tennis greats Chris Evert, Martina Navratilova, and German legend Steffi Graff.

After a crazy up-and-down year, Williams will now attempt to tie the record of 22 Grand Slam Championships set by Graff between the early 80s to late 2000s. Serena currently has 18 Grand Slams and is expected to be the favorite in all four majors tournaments (Australian, French and Wimbledon and US Open championships) thanks to a still evolving game.