Caroline Wozniacki said she felt like she never left tennis's top level after she underlined her return to form by reaching the WTA Finals semis as the only unbeaten player on Friday.
The former world number one endured a lean spell but after reaching last month's US Open final, she has been the one to watch at the end-of-season championship in Singapore.
After a tough three-setter with world number two Maria Sharapova, Wozniacki swept aside Agnieszka Radwanska and she topped White Group with a 6-2, 6-3 victory over Wimbledon winner Petra Kvitova.
Although Wozniacki, the eighth and lowest seed, is making her first WTA Finals appearance since 2011, she said did not feel like she had been away from the elite level of women's tennis.
"To me it feels like I never left really. I'm just happy to be in the position I'm in now," she told reporters. "Yeah, I never felt I was away."
Wozniacki endured a public break-up with Rory McIlroy in May but much like the golfer, who has since won two majors, the split has done her game no harm at all.
The 24-year-old Dane has since won in Istanbul and reached the US Open and Tokyo finals, and is now into the WTA Finals semis for the first time since 2009.
"I've been playing really well and doing great results and things are going well. So I'm happy and in a good place," said Wozniacki, adding that she always thought she would reach the season finale.
"That was always the goal from the start of the season. As I said before, I always believe in myself. Even though I had a little bit of a slow start to the season, I always believe.
"It just turned around and I've been playing really, really well since really Eastbourne."
It's a run that has given her hope even against her daunting next opponent, Williams, her conqueror in the US Open final and nine of their 10 career meetings.
"Well, my match-up against her so far hasn't been great. I won once and lost like 10 times, or nine, I don't know. I don't even count any more," Wozniacki said.
"But it's a new tournament. It's a new week. I've been playing well really. Again, I believe that if I play like I did today, doesn't matter who's on the other side. I can win."