SINGAPORE - Producing her best tennis on the biggest stage, Halep sent shockwaves through the BNP Paribas WTA Finals Singapore presented by SC Global, upsetting the four-time champion in just 65 minutes.
An out-of-sorts Williams could do nothing in the face of Halep's baseline precision, winning just seven points in the most one-sided of opening sets. An out-of-sorts Williams could do nothing in the face of Halep's baseline precision, winning just seven points in the most one-sided of opening sets.
She continued to chase shadows in the second and despite some belated resistance from the defending champion, it was a case of too little, too late. Halep brushed aside some final game jitters to complete a 6-0, 6-2 win when Williams found the net with a forehand.
"It's the biggest match in my life, so I can't put into words how I feel right now. I feel very happy! I just want to enjoy it," Halep said. "It was always my dream to beat one of the Williams sisters, but of course without the help of the crowd I wouldn't have been able to play this way today.
"Also my team, my Romanians, I feel so amazing right now! I will work hard for the rest of the tournament and then we will party for sure!"
Halep served well, dragged her opponent around the court with surprising ease and was ruthless in punishing anything remotely short of length. "I don't think it was her best day today, but I played really well, I was very aggressive and took the ball early, moved up the court very well, served very well - I've found my best tennis again. It's crazy!"
For Williams, one of the heaviest defeats of her career casts doubt over her future in Singapore. The last time she won so few games came in 1998 when she was defeated, 6-1, 6-1, by Joannette Kruger in Oklahoma City.
The American has won the tournament on her past three appearances and goes into her final match, against Eugenie Bouchard, facing the possibility of falling at the first hurdle.
"It's odd. I feel like once you lose you should be out of event, you know, that's what we're used to," Williams said. "But I'm still hanging in there, so we'll see what happens.
"I played the tournament when it was an elimination. This format is fun because you can lose and keep winning. But I'm in a situation where I'm going to have to win my matches because I didn't win many games today at all."
The picture looks far rosier for tournament debutante Halep, who now tops the Red Group with two wins from two matches. In her final round robin encounter she takes on Ana Ivanovic.