'What is happening': Tennis world stunned by Amanda Anisimova drama

Amanda Anisimova and Victoria Azarenka, pictured here at the Madrid Open.
Amanda Anisimova overcame Victoria Azarenka in extraordinary scenes at the Madrid Open. Image: Getty

Tennis fans and commentators were left in disbelief on Monday as Amanda Anisimova overcome an extraordinary second-set meltdown to beat Victoria Azarenka at the Madrid Open.

Anisimova appeared to be cruising towards a crushing victory in her first career meeting with Azarenka, before things went very pear-shaped.

FROSTY: Tennis world erupts over Djokovic and Nadal moment

'CLASSY': Andy Murray's incredible act for struggling Thiem

The American was up 6-1, 5-1 and served for the match at 40-0, but was unable to close out proceedings.

Azarenka then held serve and managed to break Anisimova again to make it 5-4, before more drama as the American served for it once more.

At 40-15, Anisimova missed an easy put-away volley that would have won her the match, keeping Azarenka alive once more.

But the 20-year-old finally finished things off with an ace on her sixth match point.

Anisimova dropped her racquet and looked at her box in pure relief, before becoming overcome with emotion and appearing to fight back tears.

Fans and commentators couldn't believe what they were watching.

Anisimova will now face Ekaterina Alexandrova in the last eight, after she overcame Marie Bouzkova 6-7 (4-7) 6-0 7-5.

"I think it was a really tough match, but I was playing well throughout all of it," Anisimova said afterwards.

"It was my first time playing [Azarenka] so I was really excited, and I'm just happy to get this win.

"It feels a lot better winning a match with those challenges in the end, as opposed to if it was an easy match.

"Getting through that and not letting her come all the way back, it just helps me with my confidence."

Amanda Anisimova, pictured here after beating Victoria Azarenka at the Madrid Open.
Amanda Anisimova reacts after beating Victoria Azarenka at the Madrid Open. (Photo by Robert Prange/Getty Images)

Simona Halep and Ons Jabuer advance in Madrid

Meanwhile, former World No.1 Simona Halep stepped up her French Open preparations with a 6-4 6-4 victory over Coco Gauff to march into the quarter-finals.

Halep, who won the French Open in 2018 and the Madrid title twice, is unseeded after her ranking fell last year following a series of injuries.

However she is yet to drop a set in Madrid this year and appears to be finding her best form at the right time.

The Romanian was at her aggressive best on the red clay on Monday, but was unable to break until the American teenager made a series of unforced errors to go down 5-4.

Halep, now ranked 21st in the world, served out the set but it only fired up Gauff as the 18-year-old suddenly grew in confidence.

Simona Halep, pictured here in action against Coco Gauff at the Madrid Open.
Simona Halep in action against Coco Gauff at the Madrid Open. (Photo by Burak Akbulut/Anadolu Agency via Getty Images)

Finding success at the net she raced into a 3-0 lead in the second set.

Halep quickly recovered and fought back as Gauff's error count continued to climb, breaking twice to go up 5-4 before wrapping up the contest in 77 minutes.

"I felt like I played the exactly what I had to play. In the second set she changed a little bit," Halep said in a post-match interview.

"She's been more aggressive and it was not easy to adjust, but in the end I pushed her back and I did what I wanted to do... We played a few times so I knew what to expect."

Halep will face Ons Jabeur after the Tunisian eighth seed beat Belinda Bencic 6-2 3-6 6-2 in an earlier match where the final set was played under the roof due to rain.

"Just a reminder guys, Simona won against Paula (Badosa in the previous round) and she's Spanish. So if she wins you have to cheer for me," Jabeur said.

with agencies

Click here to sign up to our newsletter for all the latest and breaking stories from Australia and around the world.