'Can't believe it': Tennis fans stunned by 'shocking' Wimbledon drama

Tennis fans were left in disbelief on Monday when big guns Stefanos Tsitsipas and Petra Kvitova crashed out of Wimbledon on the opening day.

American Frances Tiafoe caused the first major upset of the men's singles tournament by beating third seed Tsitsipas 6-4 6-4 6-3.

SO GOOD: Tennis world erupts over Federer and Djokovic twist

'HOW SAD': Serena Williams' shock announcement at Wimbledon

Tsitsipas, playing his first match since his French Open final defeat by Novak Djokovic on June 13, was on the backfoot from the beginning against a 57th-ranked opponent who took the game to him.

The Greek also went out in the opening round on his last previous appearance at the grass court tournament in 2019, when he was seventh seed. Wimbledon was not played last year due to the COVID-19 pandemic.

"It sounds pretty damn good," Tiafoe told the cheering 6000 strong Court One crowd, sheltered by a roof from the drizzle outside, as the result was read out.

"Definitely one of my best (matches). From start to finish it was pretty clean.

"This is what you train for, this is what it's all about. I live for these kind of moments. If you'd seen me on the side courts you might have seen a different performance today but I love this... got to make something good happen."

Tiafoe broke serve in the opening game and it set the tone for a match in which Tsitsipas, who had said at the weekend that he was feeling more confident on grass, showed only occasional flashes of brilliance.

But he failed to convert any of his six break points.

The American broke serve at the start of the third set, saved two break points and then had three match points on Tsitsipas' serve to wrap things up in just over two hours.

He did it on the third as Tsitsipas netted a backhand.

"I've made a ton of changes and I'm trying to just move the right way. Obviously I'm not even close to where I want to be," said the 23-year-old Tiafoe of his performances to date.

Former champion Petra Kvitova crashed out

And there was also a huge upset in the women's tournament when Sloane Stephens made a spectacular return to grass by knocking out two-time Wimbledon champion Petra Kvitova.

The American triumphed 6-3 6-4 over the 10th seed in an enthralling battle on Centre Court with the roof open after the wet weather from earlier in the day had disappeared.

Ranked 59 in the world after a difficult couple of years, Stephens produced flawless tennis at times to inspire a shock on the opening day of the championships, much to the delight of the crowd inside the All England Club again.

Kvitova was one of the favourites for the tournament and a break in the first game did little to dissuade that notion.

It was not a sign of things to come for the 2011 and 2014 champion though, with her opponent able to immediately hit back.

Stephens, in her first match on grass since she lost to Johanna Konta in the third round at Wimbledon two years ago, had settled now and forced another break in the sixth game.

The first set was closed out in 32 minutes and more blows were traded at the beginning of the second.

Again the sixth game proved pivotal with the 28-year-old from Florida having to display all of her battling qualities to save three break points and then a fourth before she held serve.

It knocked the stuffing out of Kvitova who was broken in her next game and the Czech could not get back on level terms to force a decider.

Tennis fans were left stunned by the early drama at the All England Club.

with AAP

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