Maria Sharapova made an impressive start to the Tianjin Open on Wednesday by beating Romania's Irina-Camelia Begu in straight sets.

Seeded ninth, Begu loomed as a tricky first-round opponent for Sharapova, but the former world number one from Russia swept to a 6-4, 6-2 victory.

However, two-time Wimbledon champion Petra Kvitova suffered a shock defeat, going out to local hope Zhu Lin in three sets.

Currently ranked 86th after returning from a 15-month doping ban, Sharapova -- granted a wildcard in Tianjin -- plays unseeded Magda Linette of Poland next.

The 30-year-old Sharapova, who returned to tennis in April after serving a suspension for taking the banned substance meldonium, has yet to win a tournament since then.

The five-times Grand Slam winner exited the China Open last week in the third round at the hands of Romania's Simona Halep, the newly crowned world number one.

But Sharapova had no such trouble against Begu, seeing off the 57th-ranked Romanian in 82 minutes.

The opening matches of the Tianjin Open have been badly disrupted because of rain and Sharapova said she was glad to finally get into action.

"It's been a long wait for everyone, it hasn't been easy," the Russian was quoted as saying by the official WTA website.

"I had a first practice outdoors and then I think it rained for 70 hours straight, unfortunately for the players."

Nadal races into Shanghai third round

Rafael Nadal made light work of the unseeded American Jared Donaldson to sprint into the third round of the Shanghai Masters on Wednesday.

The world number one, fresh from winning the China Open and the US Open, ruthlessly disposed of the world-ranked 56 Donaldson, 6-2, 6-1 in just 54 minutes.

Nadal, a 16-time Grand Slam winner, plays Italian Fabio Fognini in the next round.

Sloppy Federer pushed all the way in Shanghai

Roger Federer was uncharacteristicallysloppy as he fended off dogged Diego Schwartzman 7-6 (7/4), 6-4 to labour into the third round of the Shanghai Masters on Wednesday.

Federer next faces another potential banana skin in Ukrainian qualifier Alexandr Dolgopolov on Thursday.

There were 24 places in the rankings between the Swiss legend and Schwartzman and a significant height difference -- Federer towering over the 170cm (five foot, seven inch) Argentine.

But Schwartzman cut the 185cm Federer down to size and an error-strewn performance from the world number two was summed up when he squandered an easy backhand volley at the net to go to the first-set tie break.

Federer's Chinese fans, in red t-shirts and with their faces painted, were stunned.

But from 2-0 up in the tie break Schwartzman lost five points in a row and a relieved Federer clenched his fist when he finally prevailed in the set.

Unseeded Schwartzman began racking up the mistakes in the second set and Federer got an early break to put him into the next round.