Simona Halep is in the final of the US$2.4 million women's Rogers Cup for a second straight year.

The fifth seed from Romania defeated second-seed Angelique Kerber of Germany 6-0, 3-6, 6-2 in a semifinal Saturday at Uniprix Stadium in which she dominated the first half, saw Kerber find momentum midway through the second set, then took over again in the third.

Halep will play in the final on Sunday against the winner of a later semifinal between 10th seeded Madison Keys of the United States and qualifier Kristina Kucova of Slovakia.

In last year's final in Toronto, Halep retired in the third set with an illness, handing the win to unseeded Belinda Bencic of Switzerland. Her march to that final included a win over Kerber. Halep has beaten Kerber all four times they met on hard courts, but lost their two matches on other surfaces.

"It was not my day," said Kerber. "I was not playing my best.

"I made lot of mistakes. That's actually not my game. I knew I had to go for it, take chances and be a little bit risky to win against her. But she played a good match and in the end she deserved to be in the final."

There were more empty seats than usual for a semifinal on centre court, but a large contingent of flag-waving Romanian fans turned out to back Halep.

The two players took turns either dominating or struggling, with only a few games where both players looked sharp at once.

Kerber, the reigning Australian Open champion, seemed lost in the opening set, losing her first two service games thanks to an erratic serve that included three double faults. More than once the left-hander made gestures of frustration on court after misfired shots.

She gave up another break point on a double fault to fall behind 2-3 in the second set, but then broke straight back. It was Halep making angry swings that didn't quite connect with the ground after a shot into the net as Kerber held service for 4-3.

Kerber won six games in a row, including a service break to start the third set, but then Halep took over again with a break to tie it 2-2 and go on a run of six consecutive game wins to end the match.

In the final game, Kerber fought off four match points, but then saw her final shot hit the net cord, move sideways and drop perhaps a centimetre outside the line.

"She was playing more consistently than me the whole match," said Kerber. "Not like me, with a lot of ups and downs.

"I think the tournament was good for me because I had a lot of tough and close matches during the week. It was the first tournament on hard courts, so it's good to have a lot of matches before going to Rio. I'm actually feeling good. I'll take the positive things and look forward to playing at the Olympics."

Halep took a rest break and was right back out on the court with compatriot Monica Niculescu for a doubles semifinal against the Slovakian duo of Andreja Klepac and Katarina Srebotnik.

In the men's tournament, it's not getting any easier for Kei Nishikori.

Nishikori defeated Switzerland's Stan Wawrinka 7-6 (6), 6-1 on Saturday to advance to the tournament's final, but will now play either world No. 1 Novak Djokovic or 10th-seeded Gael Monfils.

Djokovic and Monfils were scheduled to play their semifinal later Saturday on centre court at York University's Aviva Centre. Nishikori has never won an ATP Masters 1000 event and Djokovic owns a 9-2 record against him. Although Nishikori has won both of his meetings with Monfils, most players on the ATP Tour consider the Frenchman as tennis's most dangerous opponent.

"I think both guys are playing great tennis right now, especially Monfils," said Nishikori. "He won Washington and I saw some of his match yesterday against (Canadian Milos Raonic.) It was great match he played.

"So I think it's going to be interesting. But, you know, haven't beat Novak for a long time on hard court so I think it's going to be a great challenge for me to play Novak again in the final, because we played in Miami and he dominated the game. So I hope I can get revenge this time."

Canadians Daniel Nestor and Vasek Pospisil faced Britain's Jamie Murray and Brazil's Bruno Soares in the doubles semifinal.

Earlier, Croatia's Ivan Dodig and Brazil's Marcelo Melo beat Romanians Florin Mergea and Horia Tecau 6-4, 6-3.

Three unforced errors were Wawrinka's undoing in the first set, with a double fault robbing him of the advantage on serve, then a forehand way wide of the court -- almost into the stands -- giving Nishikori the tiebreak set point.

Wawrinka's mental errors continued in the second set with Nishikori holding advantage for the fourth game. He missed a wide-open volley, sending the ball out of bounds when Nishikori had ceded an entire lane of the court to him.

Obviously frustrated, Wawrinka leaned on the net after the misplay, shaking his head then pulling his shirt over his face as he walked back to the baseline to the laughter of fans.

"Just missed an easy shot of the match. That's it," said Wawrinka with a smile. "You don't feel good on the court when you miss that kind of shot. It can happen, you know. At the end of the day we can all miss easy shots.

"That's not the most important shot -- I was already quite down in the second set. It wasn't easy for me to try to find any solution."