Melbourne, Australia ? Serena Williams advanced to the semifinals of the Australian Open, overcoming a sluggish start today and a back-and-forth third set to beat Shahar Peer, 3-6, 6-2, 8-6.

Williams now has won five consecutive matches for the first time since she won the last of her seven Grand Slam singles title here two years ago.

“I am the ultimate competitor,” a relieved Williams said after the match. “I feel awesome. I’m excited to be out here … I’m just so happy to be back out here competing.”

The 25-year-old American dropped her first service game and was down the break for the rest of the first set, fending off a set point in the eighth game and two more in the ninth before Peer won it with a big first serve.

Peer had only lost one point on her own serve in the second set until 30-love in the sixth game, when Williams ran off four straight points to go ahead 4-2.

The first four games of the deciding set took 34 minutes – four minutes longer than the entire second set – with Williams saving break points in the first and third games and then breaking the 16th-seeded Peer in the fourth.

But just when the former No. 1 seemed to have the match under control, Peer broke and got back on serve.

Williams faced double-break point in the ninth game, saving both with aces and then closing for a 5-4 lead with an other down the middle.

Peer broke again in the 11th game and the 19-year-old Israeli was serving for the match before Williams broke back and then held at love for a 7-6 lead.

In the changeover, Williams quickly flicked through a notebook. Whatever she read must have helped. She came out broke serve again, winning on her first match point when Peer curled a backhand out after 2 hours, 34 minutes.

Williams had 49 unforced errors and only 30 winners. But in the end, her experience counted most. Williams converted five of her six breakpoint chances, while Peer converted only three of 13.

Williams next plays 17-year-old Nicole Vaidisova, who beat fellow Czech Lucie Safarova, 6-1, 6-4, earlier today to reach her second Grand Slam semifinal.

Safarova had ousted defending champion Amelie Mauresmo in the fourth round.

“It’s great for Czech tennis to have two in the quarterfinals, one in the semis,” the 10th-seeded Vaidisova said. “Of course you don’t want to play your friend, but I’m just happy to get through.”

Top-seeded Maria Sharapova downed No. 22 Vera Zvonareva, 7-5, 6-4, Monday and will play another all-Russian match in the quarterfinals after 12th-seeded Ana Chakvetadze beat No. 8 Patty Schnyder, 6-4, 6-1.

No. 4 Kim Clijsters and three-time champion Martina Hingis will meet in the quarters here for the second straight year. Clijsters ended Hingis’ remarkable comeback in her first major after three years on the sidelines last year.

Rafael Nadal finally got to see how he holds up against a guy who can also beat Roger Federer in a match that started late Monday and finished well after midnight.

When his night’s work was done he understood what he had accomplished against Andy Murray.

“It was a very, very, very important match for me, very tough,” Nadal said. “Andy was playing at an unbelievable level. He’s very smart on court, for sure.”