For months, Swiss teenager Belinda Bencic has been tabbed as one of the rising stars on the women's tennis scene.

This week at the Rogers Cup, she showed that she can hang with — and beat — the sport's elite.

Bencic capped her improbable run to the final with a 7-6 (5), 6-7 (4), 3-0 victory over Simona Halep on a hot, sunny afternoon at Aviva Centre. Halep, who was hampered by a left leg injury, cramps and heat exhaustion, retired early in the third set.

It was yet another upset win for the unseeded world No. 20. She beat four of the top five seeds — including Serena Williams in the semifinal — to claim her first Premier-Five level title.

"It's like I cannot believe it, and it's amazing," a giddy Bencic said afterwards. "I have no words for this, and definitely talk about a tough draw."

The 18-year-old Bencic took out a murderer's row of WTA talent en route to her second career title.

Canada's Eugenie Bouchard was the first to fall. Fourth-seeded Caroline Wozniacki was next, followed by Sabine Lisicki, fifth-seeded Ana Ivanovic, the top-seeded Williams — who lost for just the second time all year — and finally the second-seeded Halep.

Bencic became the first teenager to win the $2.51-million tournament since Ivanovic took the crown as an 18-year-old in 2006. Bencic earned $456,000 with the victory and could move as high as No. 12 when the updated world rankings are released Monday.

"Now I actually feel like I belong here and that I can really be one of the top players," she said. "It's an amazing feeling."

Halep needed treatment and massage therapy at times during the match. She used ice towels and drank fluids to try to cool down and did well to force a deciding set.

But Bencic didn't let up, taking the first three games in the decisive set before Halep decided to end it.

"I was thinking that I need a miracle to finish the match," Halep said. "I knew that I had no power so I tried just to finish the match, but at 3-0 I said there is no sense to continue and I stopped."

Halep, who was looking for her fourth title of the season, earned $227,640 as runner-up. She still plans to play at next week's stop in Cincinnati.

Both players primarily stuck to a baseline game and used their strong returning skills to their advantage. Breaks were more common than holds in the early going.

Halep tried to shake out her leg pain at times in the opening set but with a 6-5 lead, she called for a trainer to work on her left quadriceps. She returned to the court with a bandage taped to the outside of her leg.

Bencic held serve and trailed 1-4 in the tiebreaker before taking control with four straight points. Halep misfired wide to set up a set point and Bencic converted when the Romanian found the net.

Down 1-2 in the second set, Halep had the trainer come out again to rub her left leg under the knee. She also had ice towels wrapped around her neck and upper legs while her blood pressure was checked.

A heat alert was in effect for the Toronto area and while the temperature was 30 C, the humidity made it feel like 37 C. It's also usually a few degrees warmer on the shadeless hardcourt.

Halep was obviously strained at times but still covered a lot of court during rallies. Instead of bending down to get ready for service returns, she stood almost upright and regularly went for winners to keep the rallies short.

The unusual approach worked and she took three straight games for a 6-5 lead, with Bencic occasionally throwing her racket to the court in frustration. But the youngster regained her composure to break Halep's serve to force another tiebreaker.

The vocal pockets of Halep supporters in the near-capacity crowd at the 8,000-seat venue seemed to spur her on and she came through with a 7-4 win.

Halep took another break before the third set and went to the locker-room before returning with a hat on her head. Bencic, who didn't seem fazed by the heat, was fuming after the interruption and voiced her displeasure with the umpire.

"I don't know why I continued to play," Halep said. "Maybe for the fans. They were like screaming all the time to push me to still play."

Bencic overpowered the fading Halep in the third set. The stunned bewilderment and raw emotion that followed her win over Williams a night earlier was replaced by a muted look as the player shook hands.

A retirement was not the way Bencic envisioned locking up her second career victory, but it was an impressive performance nonetheless.

"I stayed focused and I made the (score) 3-0," she said. "So I can be proud of how I fought today as well because I (was also) up there and I was down."

In the doubles final, the third-seeded duo of American Bethanie Mattek-Sands and Lucie Safarova of the Czech Republic posted a 6-1, 6-2 win over fourth-seeded Caroline Garcia of France and Katarina Srebotnik of Slovenia.