Determined Serena Williams has plenty left in tank

'I do have goals, but I always keep them to myself. No disappointments'

'Thank God, because if I mentioned them last year, I would've been sorely disappointed with my year this year'

The older Serena Williams gets, the more dominant she becomes. At 33, an age when most players start to fade, her grip on women's tennis looks as secure as ever.

WTA Finals: Ruthless Serena Williams avenges loss to Halep

Each time she is presented with a new challenge she finds a way to overcome it, emerging stronger each time, and her will to win is not fading.

On Sunday, she won the WTA Finals -- an elite tournament that sits just behind the Grand Slams in terms of importance -- for the third year in a row, despite concerns about her health and form.

She arrived in Singapore with an injured knee and suffered her heaviest defeat in 16 years in her group match with Simona Halep, who is 10 years her junior.

Yet, four days later, she turned the tables on Halep, spanking the World No 3 6-3, 6-0 in the final, proving yet again that she is not only the most powerful player in women's tennis, but the most determined.

"It's great. I didn't expect to end the year on this note," she said. "I was just happy to even be competing here.

"It makes everything much more sweeter and satisfying, especially for me. It wasn't my best year, but I'm just happy to have won one more title this year."

There was an element of ruthlessness about the way she disposed of Halep in the final, an ominous warning to the next generation that the world number one is as motivated as ever.

"I made so many unforced errors in our first match, and I think knowing that she has the ability and the capability to play so well, I knew that I had to step up my game," Williams said.

"I knew that I had to play a lot better, so I obviously was expecting a much better player than I was in the earlier rounds. But I think being ready for that really was able to help me out.

"It was also good for me to lose that match, because now I know what to expect next year. I really know and I'm ready for that next year. So I know what to go home and work on once pre-season starts."

That is bad news for her rivals, both present and past, as she closes in on the sport's most revered records.

Last month, she won her 18th Grand Slam singles title at the US Open, elevating her to a three-way tie for fourth with Martina Navratilova and Chris Evert. Margaret Court holds the all-time record with 24.

Williams never talks about records but is constantly reminded of where she sits. Time, rather than her opponents, now looks like her biggest hurdle.

"I never really talk about my goals," she said.

"Thank God, because if I mentioned them last year, I would've been sorely disappointed with my year this year.

"I do have goals, but I always keep them to myself. No disappointments."