Venus Williams played a brand of tennis at the Family Circle Cup that would be hard for anyone to overcome, including little sister Serena.

Venus Williams looked strong in her first clay-court tournament since 2010, defeating Jelena Jankovic 7-5, 6-0 to advance into the third round Wednesday night and continued her trek to a semifinal showdown with Serena. Don't go planning the latest all-Williams match, yet, since Venus says she's still testing her endurance after the onset of an autoimmune disease that sidelined her for more than six months.

"Actually, winning a match in straight sets is not something I'm used to yet," she said.

That's because these days, each match for Williams is a learning experience, unsure if she's got enough in the tank to compete the way she wants. That wasn't the issue against Jankovic as Williams won 12 of the final 14 games in the meeting of two former No. 1s seeking their old form.

Was this Williams' best performance of 2012?

"I don't know," said Williams, a wry smile spreading on her face. "That second set was really nice."

And the sort of showing that had plenty in the crowd of 6,908 at Family Circle Stadium dreaming of what could happen Saturday with a Venus-Serena meeting in the tournament semifinals.

"I love clay and I've won. I've won a lot of big titles on clay. Came close to winning the biggest title and it didn't work out," Venus Wiliams said. "Someone beat me."

That was Serena back in 2002, the closest Venus has come to winning the French Open.

Venus Williams fell to 134th in the world since withdrawing from the U.S. Open after she was diagnosed with Sjogren's syndrome, which left her continually fatigued. She improved to 87th after reaching the quarterfinals at the Sony Ericsson Open last week, defeating third-ranked Petra Kvitova and 14th-ranked Ana Ivanovic on the way.

Williams wasn't sure what might lie ahead on clay, a surface since hadn't competed on in two years. "I always feel like I'm stepping into the unknown," she said.

Jankovic saw the same old Venus Williams who'd won seven grand slam titles in her career. Williams broke Jankovic's serve seven times on the way to evening their career mark at 6-6.

"I didn't serve well and against Venus you have to serve well," Jankovic said.

Williams fell behind Jankovic 3-1 before taking control. Williams cracked her serves all match long, topping out at 120 mph, and hit the lines for winners throughout.

Williams' game grew stronger as the match progressed. She appeared out of sorts following a 30-minute rain delay and quickly lost the first game back to move behind 3-1.

Jankovic was still up 5-4 and was two points from the set, but mistakes — a double fault and a wide forehand — opened the door for Williams as she won the final nine games of the match.

"I think more than anything, I'm really focused, especially once I'm able to start to really get into the match," Williams said. "Then my focus and my mental game really kicks in."

Jankovic, 17th in the world and the 2007 champion here, had hoped to get more of a work out in her first clay-court event this year. Then she saw Williams waiting as her first opponent. "It's a difficult draw," Jankovic said. "Maybe if it's some other player in the first round maybe I can get a little more rhythm."

Williams, the 2004 Family Circle winner, will face Anastasia Rodionova on Thursday for a spot in the quarterfinals. Serena, who won this title in 2008, takes on Marina Erakovic in a third-round match.

Other winners Wednesday were third-seeded Marion Bartoli, who beat Russian Vera Dushevina in three tough sets, sixth seeded Sabine Lisicki, ninth-seeded Lucie Sararova, 13th-seeded Nadia Petrova and 14th-seeded Polona Hercog.

Bartoli acknowledged she's got work to do if she hopes to go even further at Roland Garros this year. Still, she was pleased that she had the mental strength to prevail in the 3 hour, 4 minute match.

"It was great to put up a fight and get the win out there," said Bartoli, the highest seed in action at Family Circle Tennis Center.

Second-seed and 2010 Family Circle champion Samantha Stosur had the day off. The scheduled top seed, Agnieszka Radwanska of Poland, withdrew from the tournament this past Sunday after taking the Sony Ericsson Open final in Key Biscayne, Fla., last weekend.

Bartoli, the 27-year-old French woman, has had her share of big victories in the past. She beat then top-ranked Justine Henin at Wimbledon in 2007 and No. 1 Jankovic at the Australian Open in 2009. Just last week, Bartoli ended the 26-match win streak of current world No. 1 Victoria Azarenka in Key Biscayne.

Bartoli has long been one of the WTA's fittest players. She's added an improved mental strength to her game, too.

Bartoli she didn't enter her match against Azarenka with the goal of stopping the streak or proving to the people she could trade ground strokes with the world's best. "I have the same motivation no matter what," Bartoli said. "That's to play my best and win."