Belinda Bencic stuns Serena Williams to reach Rogers Cup final

Swiss teenager Belinda Bencic stunned world No 1 Serena Williams to claim a place in the Rogers Cup final at the multiple Grand Slam winner's expense in Toronto.

The Swiss world No 20, who was 5-1 down at one point in the first set as it looked like Williams was going to cruise through, rallied back to win 3-6 7-5 6-4.

With the second set finely poised at 3-3, the 18-year-old found a way to tighten up her game, cutting out errors, just as more started creeping into Williams' play.

From 5-5 in the second set Bencic turned the screw, winning seven of the next eight games to turn the match on its head and give herself a 5-1 lead in the deciding third set.

Williams managed to claw it back to 5-4, but Bencic would not be denied her shock victory.

"I can't believe it now," said Bencic said. "The first set was just too fast for me, I think. But then I adapted to the game in the second set, and then I was just fighting. I mean I had 5-1 (in the third set). I'm so happy. It's amazing."

Simona Halep now awaits her in the final, having beaten Italian world No 17 Sara Errani 6-4 6-4 in the other semi.

Romanian second seed Halep beat the heat and Italian Errani.

Halep will play for her 12th career title and fourth of the year in Sunday's championship match.

Halep fell behind 0-2 then roared back to win the next four games, breaking twice to seize the lead and holding at love for a 4-2 edge. She held twice more to claim the first set in 43 minutes, taking advantage of 19 unforced errors by Errani.

In the second set, Halep opened by breaking Errani, who then broke back only to have Halep break yet again as control teetered.

Errani broke back again in the eighth game, Halep slamming her racket on the concrete in frustration after falling level at 4-4.

But then Halep forced a break, retaking the lead by winning the ninth game when Errani hit a forehand beyond the baseline, and the Romanian held serve for the victory.

"I'm completely dead now, it was a very tough match," said an exhausted Halep, who dropped to the court when Errani's return sailed long. "She played amazing, she was running everywhere for all the balls.

"I did everything I could to finish in two sets because in the third one I don't know what would happen.

"If I play against Serena tomorrow it will be a big challenge for me and I have nothing to lose."

It was the third win in four tries for Halep over Errani, having lost their first match-up at Miami in 2013 but won last year in a Doha quarter-final and earlier this year at Stuttgart.

Halep's earlier titles this season came in January at Shenzhen, February at Dubai and in March at Indian Wells.

Halep and Bencic have only met once before, with Halep claiming the victory at Wimbledon last year.