US Open tennis: No 4 seed Stefanos Tsitsipas knocked out as Serena Williams moves on

Stefanos Tsitsipas has been dumped out of the US Open. Photo / AP

The US Open has been rocked by yet another huge upset.

No 4 seed Stefanos Tsitsipas has been knocked out of the grand slam tournament after suffering a shock defeat to Colombian qualifier Daniel Galan in the first round on Tuesday.

Galan, who sits at No 94 on the ATP rankings, stunned the Greek phenom 6-0, 6-1, 3-6, 7-5 to progress through to the second round, the first time he has achieved the feat at Flushing Meadows.

Tsitsipas' performance in the first two sets could only be described as dreadful – the 24-year-old was marred by dozens of unforced errors as Galan repeatedly broke his serve.

The 2021 French Open finalist, who at one stage lost 11 consecutive games, rediscovered some momentum in the third set, but Galan booked his place in the round of 64 by winning the fourth.

Tsitsipas managed to save eight match points before finally succumbing on Galan's ninth attempt.

"He played like a world-class player and I played … close to amateur," Tsitsipas told reporters after the defeat.

"It's not very nice to say that, but that's what happened."

Serena overcomes first hurdle

Serena Williams waves to the crowd after defeating Danka Kovinic. Photo / AP

Serena Williams will get at least one more singles match in what could be the final tournament of her career.

Williams pulled away to beat Danka Kovinic 6-3, 6-3 for her record 107th victory at the US Open.

The 23-time Grand Slam singles champion advances to face No 2 seed Anett Kontaveit of Estonia on Thursday.

After her first-round victory, Williams was not ready to declare that the US Open will be her last hurrah.

Asked if this will definitively be her final tournament, Williams replied with a knowing smile: "Yeah, I've been pretty vague about it, right?"

And then she added: "I'm going to stay vague, because you never know."

When she announced three weeks ago she was ready to move on from being a tennis player, Williams indicated the US Open could be it for her, but she never explicitly said it would be.

Elsewhere, Daniil Medvedev had an easy start to his US Open title defense, beating Stefan Kozlov 6-2, 6-4, 6-0.

Nick Kyrgios romped into the second round after crushing his doubles teammate Thanasi Kokkinakis in straight sets 6-3 6-4 7-6.

Former US Open champion Stan Wawrinka has hinted that retirement is just around the corner after he was forced to abandon his first round match against France's Corentin Moutet.

Two-time grand slam champion Simona Halep was knocked out of the tournament after suffering a shock defeat to unseeded Ukrainian Daria Snigur.

Canadian tennis star Bianca Andreescu powered past France's Harmony Tan into the second round, while British icon Andy Murray marked the 10th anniversary of his maiden grand slam triumph with an impressive straight sets win over Argentina's Francisco Cerundolo.

- with AP