MELBOURNE, Australia (AP) — Appearing uncomfortable for much of the match, defending champion Novak Djokovic held on to beat David Ferrer 6-4, 7-6 (4), 6-1 Wednesday night and complete a blockbuster semifinal lineup at the Australian Open.

Djokovic leads the top four men in tennis into the semis at Melbourne Park, advancing to a matchup against No. 4 Andy Murray, who defeated Kei Nishikori of Japan earlier Wednesday.

On Thursday, No. 2 Rafael Nadal plays No. 3 Roger Federer, the first time the two former top-ranked stars have met in a semifinal since the 2005 French Open.

It marks only the third time that the top four seeds have advanced to the semis at the Australian Open — it previously happened in 1988 and 2005. It was also the 14th time at all Grand Slams since the Open Era began in 1968, but the third time in the last four majors, including the U.S. Open and French Open last year.

Djokovic rubbed the back of his upper left leg on several occasions, looked on the verge of being physically sick in the second set and buried his head in towels several times during breaks. During the third set, a tired-looking Djokovic sat down on a linesman’s chair during a line-call video challenge by Ferrer.

“I was lucky to get out of the second set, it was a big mental advantage to get two sets up,” Djokovic said.

He also played down talk of any injuries.

“I don’t have any physical issues,” Djokovic said. “I feel very fit and I feel mentally, as well, very fresh.

“It’s just today I found it very difficult after a long time to breathe because I felt the whole day my nose was closed a little bit. I just wasn’t able to get enough oxygen.”

Ferrer said he couldn’t be sure if Djokovic was healthy — or not.

“No, I don’t know,” Ferrer said. “You have to ask to him, not me. He ran perfect all the match. Nothing special.”

The Nadal-Federer semifinal matchup has been rarely possible because the pair held the top two spots for most of the time between 2005 and 2010, meaning they could only meet in the finals after being placed in opposite sides of the draw.

Djokovic said he’d be watching the Nadal and Federer match like any tennis fan.

“I will enjoy it from my couch, they’re two out of four or five of the greatest players to play this game, they’ve been so dominant,” Djokovic said. “Every time they play it’s a treat. I’m going to have a nice dinner at home and watch them.”

Murray, for his part, is also surprised to be not facing Nadal in the semifinals.

“It has been amazing, I pretty much drew to be in Nadal’s half … almost every Slam,” Murray said. “I can’t remember the last time I wasn’t in his half of the draw. It’s been a long time.”

On the women’s side, former and reigning Wimbledon winners Maria Sharapova and Petra Kvitova — two of the three players who can take the No. 1 ranking — advanced to the semifinals.

Sharapova won 6-2, 6-3 on Wednesday against fellow Russian Ekaterina Makarova, who knocked out five-time champion Serena Williams in the previous round. Kvitova reached the semifinals at Melbourne Park for the first time with a 6-4, 6-4 win over unseeded Italian Sara Errani.

The other player who can reach No. 1 — third-seeded Victoria Azarenka — plays defending champion Kim Clijsters in the other semifinal Thursday.