Melbourne: Novak Djokovic must have been relieved to have given his weary legs a relatively quick workout on Tuesday with 6-1, 4-6, 6-1, 6-4 victory against Czech fifth seed Tomas Berdych in the Australian Open quarter finals.

Berdych appeared quietly confident. He had entered the tournament with his highest grand slam seeding of five. He had barely been pushed throughout his first four rounds. His longest match had been two hours, 44 minutes against Kevin Anderson, and that was really only extended by a marathon third set tiebreak that he clinched 15-13.

If ever there was a time for him to claim his second career win over the Serb, and first since their 2010 Wimbledon semi-final, it was at Melbourne Park on Tuesday.

Djokovic had different ideas. He hid any signs of fatigue, bounced on his toes throughout and effortlessly scrambled and slid across court to advance to a semi-final against Spain’s David Ferrer. “Obviously, it’s not easy to always be at your 100 percent fitness,” Djokovic said following the 2-1/2 hour win. “But after a five-hour match two days ago, I was quite convinced I could recover for this one.

“I felt good enough to go another five hours. But I definitely wasn't thinking about it. I tried to get the work done as fast and efficiently as possible. I was very happy with the way I started the match. Very aggressive out there, going for my shots, which wasn’t the case against Wawrinka. “So it’s a good improvement and very encouraging for my next match.”

Maria Sharapova’s semi-final opponent will be Li Na, who beat Agnieszka Radwanska 7-5, 6-3 in the first of Tuesday’s quarter-finals, breaking the Polish player’s 13-match winning streak to start the season.

The No. 4-seeded Ferrer survived once in the third set and twice in the fourth when No. 10 Nicolas Almagro was serving for the match, holding firm to finally advance to his fourth semi-final in six Grand Slam events with a 4-6, 4-6, 7-5, 7-6 (4), 6-2 win.

The 30-year-old Li advanced to her third semi-final in four years at Melbourne Park. “She’s a tough player. I was feeling today against a wall,” said Li, who lost the 2011 Australian Open final to Kim Clijsters only months before her Grand Slam breakthrough at the French Open.

The first man through to the semi-finals at Melbourne Park had a difficult time. “It was a miracle I won this match, I think,” Ferrer said. “I tried to fight every point; that’s my game. I always fight.”

Almagro dominated the first two sets and was serving for the match in the third when Ferrer bounced back, breaking in the crucial 10th game and then breaking his Davis Cup teammate again. The fourth set featured eight service breaks, and Ferrer finally took control in a tiebreaker to force a fifth. Almagro has played 33 consecutive major tournaments, but never reached a semi-final. (agencies)