Unseeded Belarusian Victoria Azarenka reached her first Grand Slam semi-final since 2013 with a 6-1 6-0 win over Belgian 16th seed Elise Mertens.

On Wednesday, Azarenka took advantage of an awful display by Mertens.

She broke her opponent six times in total to complete a stunning victory in only 73 minutes.

The recent Western & Southern champion will now face old foe Serena Williams, whom she has played 22 times but only beaten on four occasions.

"I'm so excited about this amazing opportunity to play a champion, someone I respect a lot and who's my friend," she said. "I hope it will be fun - it'll be fun for me."

Azarenka rolled back the years with some of her groundstrokes, especially the powerful double-handed backhand down the line, and she was also helped hugely by a below-par Mertens.

The 24-year-old Belgian was exceptional against Australian Open champion Sofia Kenin in the previous round, but it was a different story on Wednesday as she produced woeful service statistics - winning 14% of points on her second serve in the first set - compounded by several errors on her forehand.

They broke each other early in the match before the former world number one repeated the trick twice more courtesy of her opponent's double fault and then her own excellent backhand down the line.

After taking the first set, Azarenka adopted a zen-like pose on her chair. While the Belarusian appeared relaxed on resumption, Mertens looked anything but and yet again another double fault led to her being broken in the opening service game of the second set.

Her game had fallen apart as Azarenka broke twice more en route to setting up a mouth-watering semi-final against Williams on Thursday.

Azarenka overcomes personal battles to return to elite level

It has been a long and difficult journey to get back to this level for the current world number 27.

After having her son she was involved in a custody battle with his father, following their split. That resulted in withdrawals from tournaments, including the 2017 US Open and 2018 Australian Open.

She eventually returned to the WTA Tour and the top 100 in 2018 but was struggling to venture past the third round at any of the majors.

And only last week, Azarenka revealed she had almost quit the sport before the coronavirus pandemic because of a personal issue, stating she had not touched a racquet in five months.

But her focus returned to tennis and now she is on an 11-match winning streak.

After her win on Wednesday, she said: "I didn't think I ever enjoyed tennis - it was a job. When I lost I couldn't function for two days, but now it doesn't bother me."

Azarenka also said she was enjoying her time in New York, despite the restrictions and lack of crowds.

"I'm able to enjoy it," she added. "I'm happy to have a house here, with my mum cooking and the chance to be able to play with my son in the garden and push him on the swings."