Belinda Bencic defeats Angelique Kerber in Cincinnati

Swiss teenager Belinda Bencic maintained her recent giant-killing form in Cincinnati with a battling 7-5 6-3 win over higher-ranked German opponent Angelique Kerber on Tuesday.

Bencic, 18, is brimming with confidence after winning in Toronto at the weekend after a tournament which included a stunning semi-final defeat of Grand Slam-chasing world number one Serena Williams.

The teenager, coached by Melanie Molitor, mother of Martina Hingis, said she was pleased with her mental strength after recovering from 5-1 down in the first set to defeat 11th seed Kerber.

"I'm so happy that I could win," she said of her Toronto title. "It was very nice from the crowd, the great atmosphere on the court. I just tried to fight for every point.

"It's amazing that I could beat so many players so high ranking and top players in the same week.

"I think I definitely improved my tennis, and I hope I can bring it also to here."

Bencic, whose ranking has now reached 12 after her win in Toronto, reeled off four games in succession to level the first set 5-5 after trailing early on to Kerber.

I just look from match to match. I would never expect to be number 12 right now.

She then broke for 6-5 and took the set a game later. In the second, she began with a break on the way to the win.

"I don't need to adjust my goals," she said. "I just look from match to match. I would never expect to be number 12 right now."

Elsewhere, Sloane Stephens took down another seed as she beat number 10 Carla Suarez Navarro 6-1 6-2.

France's Kristina Mladenovic overcame Daniela Hantuchova 6-2, 6-1, while Flavia Pennetta defeated former Australian Open finalist Domenika Cibulkova 7-5 6-2.

Mona Barthel beat Australian Casey Dellacqua in a 2-6, 6-3, 7-6 (7/4) comeback while Caroline Garcia beat Sabine Lisicki 3-6 6-3 6-4.

Former number one Victoria Azarenka reached the second round 6-1 6-2 over Lauren Davis.

But the Belarus player hinted at a medical issue which she refused to specify, only to say that she is now working with doctors to deal with it.

"I would just like to keep it for myself at the moment. I'm fine, I'm not in danger. I'm not sick or something," she said.