Serena Williams, her insatiable will to win as strong as ever, regained her composure after smashing her racquet and being on the brink of defeat to beat Caroline Wozniacki 2-6 6-3 7-6 yesterday and reach the title match at the WTA Finals.

The world number one will face Simona Halep in today’s final after the pint-sized Romanian crushed Poland’s Agnieszka Radwanska 6-2 6-2 in the second semi-final.

Halep also demolished Williams during the round-robin stages earlier in the tournament, setting the stage for a mouth-watering rematch with the world number one.

The best of friends off the court, Williams and Wozniacki slugged it out like two prize-fighters for almost two-and-a-quarter hours until Williams delivered the killer blow to end a contest filled with drama and escalating tension.

The American looked to be on the ropes after losing the first set and smashing her racquet in frustration, then falling 5-4 behind in the third set.

But Wozniacki, who lost to Williams in last month’s US Open final, blinked first, missing her chance to serve out the match and the American made her pay by going on to win the deciding tie-breaker.

“Being so close and still losing, it really sucks,” Wozniacki said.

“But, you know, I think it was a great match. I played all I could today. I played my heart out. I fought until the end.”

Williams only snuck into the semi-finals on a countback but is suddenly back on track to win the elite season-ending event for the third year in a row.

Halep, one of the most improved players in the women’s game, showed no mercy against Radwanska, breaking her serve five times and racking up 26 clean winners in her lopsided win.

Ranked 64th in the world 18 months ago, she made her first grand slam final at the French Open earlier this year and now her first WTA Finals decider in her maiden appearance at the elite event.

“I’m very excited to be in the final,” Halep said.

“I think I’ve played my best tennis here this week.”