08/13/2011 12:32 EDT | Updated 10/12/2011 05:12 EDT

Serena Williams continues comeback, books her berth in semifinals at Rogers Cup

TORONTO - Two consecutive nights, two gruelling see-saw battles.

Serena Williams took another step on her road to recovery Friday, but it's not a path her opponents have exactly been laying neatly at her feet in Toronto.

The 29-year-old American star, who's been sidelined by injury and illness for the better part of a year, booked her spot in the semifinals at the Rogers Cup with a hard-fought 4-6, 6-3, 6-2 victory over Lucie Safarova of the Czech Republic on Friday evening.

The match that stretched two hours and four minutes came a night after Williams had to battle back from a set deficit to beat China's Jie Zhang, also a two-plus hour match.

Good thing the 13-time Grand Slam champ upped her fitness regiment in her comeback bid.

"I just decided if I can be fit, that can be a new level in my game, because I've always been — I think — a halfway decent player," Williams said. "So I thought, OK, what haven't I done? I've never really been fit. I'm still not super fit, I always have cream sodas at night. But I've been doing some running. I hate running, but I've been doing more running, distance running."

Williams will face No. 4 seed Victoria Azarenka of Belarus in Saturday's semis after Azarenka, the highest-seeded player remaining in the women's draw, breezed by unheralded Galina Voskoboeva of Kazakhstan 6-1, 6-2 earlier in the day.

No. 10 Samantha Stosur of Australia will meet 13th-seeded Agnieszka Radwanska of Poland in the other semifinal. Stosur downed Italy's Roberta Vinci 6-4, 6-1, while Radwanska defeated No. 11 Andrea Petkovic of Germany 6-4, 6-3.

Williams' victory surely prompted sighs of relief from tournament organizers Friday night, the end of a long week that had seen the star power all but fizzled out with 11 of 16 seeds falling. Williams is unseeded after nearly a year away from the game, but is easily the biggest star remaining.

Williams is playing just her fourth tournament since she was injured shortly after winning her fourth Wimbledon at All England Club last summer.

A few days after that victory, she cut her foot on glass at a restaurant in Germany, which would require two operations. She spent 10 weeks in a cast and 10 weeks in a walking boot. Then she was diagnosed in February with blood clots in her lung.

She didn't return to the practice court until April.

"I definitely feel like I'm coming back from a layoff, it trips me out that this is only my fourth tournament. A lot of people are still expecting me to be at the top level and I expect it even more," she said.

Regaining her confidence, she said, has been the most difficult part of her return to the world stage.

"I had to pray for confidence. I could go out there and no matter what I'm ranked, people still expect me to win sometimes and do really well. I was just not there, just trying to get there. Once I hit Stanford, I was there man, my prayers were answered," said Williams, who won the Stanford Classic late last month.

She struggled with her forehand, and Safarova's left-handed serve, in the first set, but poured it on the second. And by the time she broke Safarova's serve to go up 3-2 in the third, the momentum was all Williams, who fired eight aces on the night.

"My forehand is by far my favourite, and once I punched myself in the head I started hitting them way better in the last few games, I just had to get over what I was going through and so I came back. That was good," Williams said.

Williams had the Rexall Centre crowd chuckling after the match when she disclosed her plans for the evening had she not won. She had planned to go to sing karaoke.

"Air Supply . . .," she said. "I'm in a real '80s mood right now."

Azarenka's victory over Voskoboeva, meanwhile, ended a coming-out party for the underdog Kazakh, who's ranked just 135th in the world. Voskoboeva had upset No. 9 Marion Bartoli, Flavia Pennetta and fifth-seeded Russian star Maria Sharapova to earn her quarter-final berth.

But Azarenka dismissed her opponent's string of success in the same straightforward manner with which she dispatched the 26-year-old in the 69-minute match.

"It's one week," Azarenka said. "If she can do that on a consistent basis, she'll be up in the top-10."

The 22-year-old Azarenka — who's yet to drop a set in the tournament and has lost just six games — focused her mind on her match by dancing to music on her iPod.

Then she relentlessly charged past her Russian-born Kazakh opponent, claiming six break points against Voskoboeva, who showed her frustration by firing a ball that narrowly missed hitting a ball boy.

The 5-11 Azarenka said her opponent's hot streak never had her concerned.

"Worried? No. Of course, I had to take into consideration that she'd been playing really well, but I was more focused on my game and trying to execute my shots and less on the opponent's game," she said. "It really worked out well that I focused more on me than on her."

Meanwhile, Stosur, ranked 11th in the latest WTA rankings, broke Vinci's serve while leading 5-4 in the first set to grab the edge.

The Australian then poured it on against the 22nd-ranked Italian in the second to move into the semis in convincing fashion.

"As the match went on, I obviously probably grew in confidence, and then you get that bit of a lead with a buffer of a couple breaks and felt like I could maybe start going for a bit more," Stosur said. "I went for some big ones and it paid off.

"Semifinals, you've got to believe that anything in possible," she added. "Having said that, from semifinals to winning the tournament, there's a still a long way to go, but I think in this position you've got to. If you don't, then it's probably a little bit silly."

In a battle of versatility over power, the 22-year-old Radwanska took an hour 41 minutes to dispatch Petkovic, winning the final long rally when the 23-year-old German fired a shot into the net.

Radwanska is battling a shoulder injury, which she summed up to "too much tennis." The right-handed Polish player wore a patch the size of a saucer taped over her right shoulder.

"Playing every day is not very helpful with my shoulder," Radwanska said. "Still I can handle it, and for sure I will do my best (Saturday)."

Petkovic wasn't surprised by the long rallies with Radwanska, but given the opportunity to re-play the match, would have taken an entirely different approach.

"You really have to build up to point and I think I played too much flat to her, maybe I should have used the angles more, but that's something you realize after the match," Petkovic said. "Today I just felt like I needed to overpower her which was the wrong approach."

Petkovic, one of the most engaging players at the Toronto tournament, showed a more surly side of her personality after losing the first set. She slammed her racket into her bag and then slumped with scowl into her seat, slapping one arm of the chair.