The temperatures in Melbourne may be mercifully mild, but on court the Australian Open is now beginning to heat up. Certainly that was the case for Roger Federer on Friday. The in-form second seed and 18-time Grand Slam champion suffered a stunning upset loss to unseeded Andreas Seppi in the third round offer a reminder to every big name remaining that that there is little room for comfort with the competition only getting tougher from here.

Of course, the first week had already provided plenty of drama for the top seeds. On the women’s side fifth seed Ana Ivanovic was dumped just over three hours into the first day’s play, while world No. 2 Maria Sharapova had to save two match points in her second-round encounter. It has been a similar story for the men, with Rafael Nadal battling back to claim a dramatic five-set win in his second round match against American qualifier Tim Smyczek. Nadal’s progress was much smoother in booking his place in the fourth round, where he’ll take on big-serving South African Kevin Anderson on Sunday. The only previous meeting of the two 28-year-olds came in 2010 when Nadal triumphed in straight sets.

Two men with a much more recent rivalry will also face off in what, on paper, is the pick of the men’s last 16 matches. Andy Murray, looking to return to Grand Slam contention, will take on the player who ended his Wimbledon title defense last year, Grigor Dimitrov. It is the three-time Australian Open runner-up Murray who has looked the more impressive so far, while Dimitrov, still looking for his Grand Slam breakthrough, struggled in a five-set win against Marcos Baghdatis in the third round.

Still among those yet to play their third round is top seed, and now even stronger favorite to take the tile after Federer’s exit, Novak Djokovic. The four-time champion in Melbourne will take on experienced Spaniard Fernando Verdasco in Saturday’s evening session on Rod Laver Arena, with the winner meeting either American John Isner or Gilles Muller. Meanwhile, defending champion Stan Wawrinka will seek to remain on course for a semifinal meeting with Djokovic when he takes on Jarko Nieminen in the third round.

Saturday’s play also sees the top seed in the women’s event, Serena Williams, look to book her place in the last 16 when taking on Ukraine’s 26th seed Elina Svitolina. The American, going for her 19th Grand Slam to surpass Chris Evert and Martina Navratilova on the all-time list, has failed to make it past the quarterfinals in her last three visits to the Australian Open but won her only previous meeting with 20-year-old Svitolina. Also in the women’s third round, Williams’ compatriot, the up and coming Madison Keys, will look to upset Wimbledon champions Petra Kvitova.

In the fourth round the following day, Sharapova will aim to keep her hopes alive of winning a second title Down Under and of leapfrogging Williams for the world No. 1 when going up against China’s 21st seed Peng Shuai.

TV schedule Friday, Saturday and Sunday:  The Tennis Channel will provide coverage between 7 p.m. EST and 9 p.m., before switching to ESPN2 for the remainder of the day’s play.

Live stream: ESPN3