Remarkably, Serena Williams arrived back on home soil for the North American hardcourt stretch with just one defeat to her name all season. That came against Petra Kvitova in Madrid, and while surprising, was not altogether unexpected. Few, though, could have predicted the second player to blot the World No.1’s copybook.

Belinda Bencic had long been touted as one to watch from the WTA’s emerging crop of talented youngsters, a seamless transition from junior prodigy to professional success doing little to downplay the hype.

Last September she made her first waves in the senior ranks, reaching the US Open quarterfinals, before making a further breakthrough this summer by lifting the title in Eastbourne.

After losing early in Washington DC, the 18-year-old headed north of the border looking to build some momentum ahead of her return to Flushing Meadows. What transpired, surpassed even her own lofty expectations, as wins over former World No.1s Caroline Wozniacki and Ana Ivanovic set up a semifinal meeting with the current incumbent.

In her three career encounters with members of the Top 3, Bencic had lost comfortably, and when Williams briskly pocketed the opening set this trend looked set to continue.

Unlike so many of Williams’ opponents, the Swiss had no intention of going quietly. In their previous meeting, last spring in Madrid, Bencic had won just three games, but the exuberance of youth and those recent accomplishments seemed to imbue her with the confidence to stage a remarkable recovery.

The last two times the Rogers Cup was staged in Toronto, Williams walked away with the title, but in the second set it was Bencic looking like the serial champion, hurtling into a 5-3 lead. One particular rapid-fire exchange at the net was reminiscent of Martina Hingis at her flowing best.

Williams rallied, but was unable to prevent the teenager leveling the match. In the decider, Bencic went for the jugular, surging into a commanding lead once more.

As the finishing line approached, the Swiss looked like in danger of wavering. Luckily for her, Williams, was even tenser. In the final game, Bencic delivered a driving backhand to reach match point, then making no mistake with a forehand winner to seal the biggest win of her fledgling career.

“I can’t describe the feeling right now,” Bencic said. “I was very overwhelmed from the situation on the court, but I’m just so happy the forehand landed in and she couldn’t reach it anymore.

“It was an incredible feeling. I have no words.”