Wang Qiang's impressive run at the U.S. Open continued on Sunday as the Chinese 18th seed powered into the first Grand Slam quarter-final of her career after displaying grit and poise to stun reigning French Open champion Ashleigh Barty. 

Second seed Barty, who beat Wang twice last year in their only prior meetings, committed 39 unforced errors in this shocking 6-2, 6-4 loss, but she still found some positives after the draining encounter. 

"It's a tough day at the office today. But it has been a year where we've hit our goals," Barty said. "We've had a great season in Grand Slams for singles. We've made the second week every single one, which has been really special."

Wang, who had squandered four match points in a semi-final loss last week at the WTA Bronx tournament, was overwhelmed with joy. 

I'm so happy I won. I think I'm really focused on the court, really enjoyed the way I played," she said. "I did really well today. I'm really mentally strong today. Just keep going."

The 27-year-old Wang is only the third Chinese woman to make the quarter-finals at Flushing Meadows since Peng Shuai made her breakthrough in 2014. he credited her former coach Peter McNamara, who died in July of prostate cancer, with helping her beat the odds. 

"He helped me a lot. It was really tough to [sic] me to hear he passed," Wang said. "I think he has always been there with me." 

Wang had worked with McNamara since 2015 until the start of this year, when the Australian's deteriorating health made it harder to travel, ending a partnership that coincided with her cracking the top 20 last season. 

"He told me how to play the match. He took me to the professional tennis. So that's how he taught me," Wang added. "He always believed in me. He told me I can be the top player." 

Next up for Wang is eighth-seeded Serena Williams, who remained on course for a record-tying 24th Grand Slam title after outclassing Petra Martic 6-3, 6-4 later on Sunday.

Meanwhile, Johanna Konta avenged her Rome final loss to Pliskova in May, beating the Czech third seed for just the second time in eight tries, 6-7 (1/7), 6-3, 7-5. 

The British 16th seed has raised her game at the Slams this season, and is enjoying her best run at Flushing Meadows, having twice reached the fourth round. 

"To go one step further is a massive achievement for me and I'm really hoping to make that one, two, three steps forward," Konta said. 

Pliskova, the 2016 US Open runner-up, saw her hopes of returning to world number one this fortnight extinguished by the loss. 

"She (Konta) played extremely well at some points. Of course, I had my chances, maybe the set and break. I didn't play that well there," Pliskova said. 

On the men's side, five-time champion Roger Federer stretched his record for Grand Slam Open era quarter-finals appearances to 56 by overwhelming Belgian 15th seed David Goffin 6-2 6-2, 6-0 in only 79 minutes. 

"It's definitely very special to be playing for these records," Federer said. "Being in my 56th quarters now of a Slam is definitely a nice feeling." 

Federer's 13th appearance in the US Open quarter-finals, four shy of the record 17 by Jimmy Connors, will come Tuesday against 78th-ranked Bulgarian Grigor Dimitrov. 

(With input from agencies)