LOS ANGELES: Seven-time Grand Slam Champion Venus Williams powered into the third round of the WTA clay court tournament at Charleston on Wednesday with a 6-4, 6-2 victory over Alison Riske.

Williams, seeded third and seeking a 50th career WTA title this week, fired 20 winners, displaying a sharp service game in a match lasting less than 90 minutes.

Things didn’t go so well on the green clay of Charleston for second-seeded Swiss Belinda Bencic, beaten 6-1, 6-1 by Russian Elena Vesnina.

Bencic, the world No. 10, appeared to be struggling with the same back trouble that forced her out of her opening match in Miami.

Vesnina took full advantage, advancing in just 56 minutes.

She’ll next face Lourdes Dominguez, who reached the third round when Canadian Eugenie Bouchard retired with an abdominal injury.

Spain’s Dominguez was leading 6-4, 1-6, 1-0 when Bouchard decided she couldn’t continue.

“It’s the same one (from last year), which is why I’m concerned and why I did retire,” said Bouchard, who played at last year’s Wimbledon with an abdominal muscle tear and said she didn’t want to repeat the mistake of making the injury worse.

Williams’ win was relatively straightforward, although the 35-year-old coming off opening match defeats at Indian Wells and Miami said it “wasn’t easy.”

“I think experience definitely helped,” said Williams, who won the Charleston title in 2004. “She has played good matches and won titles, so just the experience of playing those important points helped me a little more today.”

Williams next faces Kazakhstan’s Yulia Putintseva for a place in the quarterfinals.

Putintseva defeated 15th-seeded German Sabine Lisicki 7-5, 4-6, 6-3.

In other matches on Wednesday, seventh-seeded American Sloane Stephens defeated Danka Kovinic 6-4, 6-3, but former Charleston finalists Lucie Safarova and Madison Keys both bowed out.

America Louisa Chirico sent fourth-seeded Safarova packing 6-3, 6-3, while Germany’s Laura Siegemund rallied for a 6-7 (3/7), 6-4,6-4 win over eighth-seeded Keys.

Monaco topples Paire

Argentina’s Juan Monaco ousted second-seeded Benoit Paire of France 6-3, 7-5 on Wednesday to reach the quarterfinals of the ATP clay court tournament in Houston.

Monaco, the 2012 champion in Houston, notched a second straight tour-level win for the first time since Nice 13 months ago.

He saved 10 of 12 break points he faced and improved to 3-1 against Paire, the world number 22.

The 32-year-old Monaco booked a quarterfinal clash with fifth-seeded American Sam Querrey, a 6-3, 6-3 winner over Germany’s Benjamin Becker.

Querrey belted 13 aces and saved the only two break points he faced to overcome Becker in just 50 minutes.

Querrey faces a tough matchup against Monaco — he has never beaten the Argentinian in three prior meetings on clay.

Top-seeded American John Isner advanced on cue, defeating American Denis Kudla 7-6 (7/2), 7-6 (7/4).

Isner next faces young South Korean Chung Hyeon, who rallied for a 5-7, 6-2, 6-2 victory over US wildcard Tommy Paul.

Defending champion and fourth seed Jack Sock of the United States launches his campaign on Thursday with a second-round match against Australian qualifier Matthew Barton. Third-seeded Feliciano Lopez and seventh-seeded Marcos Baghdatis will also be in action on Thursday.