World number four Elina Svitolina withdrew from the Hong Kong Open with a leg injury on Thursday, the latest blow to the WTA event which has also been hit by several pre-tournament pullouts and early exits.

The top seed’s withdrawal means her second-round opponent, American world number 114 Nicole Gibbs, receives a walkover into the quarter-finals.

Ukraine’s Svitolina, who is due to play this month’s WTA Finals in Singapore, has been carrying a right groin strain which was heavily strapped as she laboured to a first-round victory over Kazakhstan’s Zarina Diyas on Tuesday.

Svitolina told AFP that she sustained the injury during her mammoth, 3hr 21min quarter-final defeat in Beijing last week to the eventual champion there, Caroline Garcia.

“I picked up the injury a little bit in Beijing,” she said. “It’s the groin. All the time when I go for wide shots or stretch I feel it.

“I will probably do some scans now to see how it is, because you know I have Singapore. It’s a tough decision because I really wanted to play here.”

Svitolina’s exit is just the latest to affect the tournament, which was rocked before it started by the pullouts of three big names.

US Open champion Sloane Stephens cried off with an injury after losing in the first round in both Wuhan and Beijing, her only appearances since her Flushing Meadows triumph.

British world number 10 Johanna Konta also cancelled her trip because of a foot problem, while France’s 13th-ranked Kristina Mladenovic opted out with a knee injury.

Of the star players that did show up at Victoria Park, number two seed Venus Williams was sent packing in her second-round match in straight sets on Wednesday by Japanese teen sensation Naomi Osaka.

And she was swiftly followed by fourth seed Agnieszka Radwanska of Poland, beaten in three sets by the resurgent former US Open champion Sam Stosur.

It leaves in-form defending champion and world number six Caroline Wozniacki as the highest-ranked player remaining and odds-on favourite to retain her crown.

Wozniacki, who won in Tokyo just two weeks ago, faces little-known Australian Lizette Cabrera, the world number 155, for a place in the quarter-finals later on Thursday.

Svitolina has been enjoying the best season of her career, winning five times on the WTA Tour in Taipei, Dubai, Istanbul, Rome and Toronto while breaking into the top 10 for the first time and hitting a career-high ranking of three.

The Ukrainian now has just 10 days to recover her fitness before the top eight-ranked players battle it out in the season-ending WTA Tour finals.

In the quarter-finals, Gibbs will face either fellow American Jennifer Brady or China’s eighth seed Zhang Shuai, who play later on Thursday.