WUHAN - Maria Sharapova's comeback from a leg injury lasted less than three sets on Monday before she retired with a left forearm problem against unseeded Barbora Strycova at the Wuhan Open.

The world number three had been out with a persistent leg injury since July, when she lost a Wimbledon semi-final to Serena Williams, and pulled out of three events including the US Open. But the Russian's long-awaited return proved short-lived as she was pushed to two tie-breaks by the Czech Republic's Strycova before withdrawing when 2-1 up in the third.

"I got pain in my left forearm. It just got worse and worse as I continued," Sharapova said after the match. "I don't remember the last time I redrew in the middle of a match. It's not a nice feeling," she added. "Unfortunately it's sad that Maria couldn't finish the match because I thought it was a really good match," Strycova said of her opponent. "It's never easy (against Sharapova) because she's playing very long and very powerful. So you have to watch out not to make so many mistakes." Sharapova's retirement leaves a question mark over the rest of her season with only one big tournament, the China Open, left before the year-ending WTA Finals in Singapore. She had pulled out of a WTA event in Toronto and the Cincinnati Masters hoping to be ready for the US Open, but was also forced to withdraw from the year's final Grand Slam tournament. "Obviously Singapore and Fed Cup is a big priority for myself. I'll do everything in order to be healthy for that. I don't know how long it will take for this to recover so I can't really give myself or you a definite answer about next week," Sharapova said.

The other upset of the day saw the late withdrawal of Canadian Eugenie Bouchard linked to ongoing symptoms from the concussion suffered at the US Open earlier this month. Bouchard's pullout left Swiss youngster Belinda Bencic -- who this year earned a reputation as a giant-killer after knocking out top ranked players including Serena Williams -- to play lucky loser Ajla Tomljanovic of Croatia. A visibly tired Bencic had to fight hard for a two set win over Tomljanovic, just a day after the 18-year-old lost the final of the WTA Pan Pacific Open in Tokyo to Agnieszka Radwanska.

Bencic will be hoping for a strong performance at Wuhan, which could see her end the year in the top 10 cementing her rapid rise up the rankings over the last two years. Radwanska did not fare so well against Venus Williams, losing in two sets to the former world number one, 6-1, 7-6 (7/4). Eighth seed Karolina Pliskova downed Croatian Mirjana Lucic-Baroni in a closely fought three sets in the second round, while this year's shock finalist at the US Open Roberta Vinci of Italy took three sets to knock out qualifier Danka Kovinic of Montenegro 5-7, 6-1, 6-3 in the first round.

Seventh seed Serbian Ana Ivanovic downed Alexandra Dulgheru of Russia in two sets, breaking Dulgheru's serve in the final game to end 6-1, 6-3, and will meet in the second round unseeded Madison Brengle of the US who beat Slovakian Dominika Cibulkova in straight sets.