MELBOURNE, Australia — Defending champion Roger Federer advanced to the Australian Open semifinals with a 6-1, 6-3, 6-3 win over Stanislas Wawrinka today in a mismatch that had all the intensity of a practice session.

Caroline Wozniacki had a significantly tougher assignment, rallying from a set and a break down to beat French Open champion Francesca Schiavone 3-6, 6-3, 6-3 and secure her spot in the semifinals — and at the top of the rankings.

Schiavone dominated the opening set and a half before the effects of her previous match kicked in. She beat Svetlana Kuznetsova in a three-set match lasting 4 hours, 44 minutes, a record for a women’s Grand Slam singles match.

Wozniacki will face Li Na, who beat Andrea Petkovic to reach back-to-back Australian Open semifinals.

“Francesca is such a fighter, and she started off really, really well and I didn’t feel like I had the right timing,” Wozniacki said. “So it was difficult for me in the beginning, but I fought back and I’m so happy that I’m standing here as the winner of the match.”

Wozniacki is playing her first major with the No. 1 ranking, a position that has been called into question because she’s never won a major. She held her nerve despite some shaky moments at the end, finishing off Schiavone on her fourth match point, nine minutes after first serving for the match.

Federer, aiming to become the first man to win five Australian titles, was playing in his record-tying 27th consecutive Grand Slam quarterfinal when he met Wawrinka in the first all-Swiss quarterfinal at a major.

No. 19 Wawrinka was playing at this stage for only the second time at a major. Making it worse, he had only beaten Federer once in their seven previous matches.

Federer and Wawrinka combined to win the Beijing Olympics doubles gold medal for Switzerland and have been Davis Cup teammates. So meeting on such a big stage had challenges for both men.

“I play Stan obviously very different to what (Andy) Roddick or (Gael) Monfils or what other players might do against him. Clearly it’s not an easy match for him also,” said Federer, now into his eighth consecutive Australian Open semifinal. “I’ve been in so many quarterfinals, in this situation so many times before, that I have the experience and I have the game to, you know, be tricky for him.

“The scoreline suggests maybe it was easier than it looked like. I thought it was a pretty tough match.”

Wawrinka had only one look at a break chance against the 16-time Grand Slam winner, in the sixth game of the second set, and lost three straight points to let Federer off the hook.