The tennis world is still in shock over Serena Williams' defeat.

After looking like a shoo-in for a berth in at least the final four, Williams was ousted in the fourth round Monday to Russia’s Ekaterina Makarova (6-2, 6-3) because of 37 unforced errors and a first-serve percentage that was barely over 50 percent.

Aside from Williams, the women’s side has held to form.

On the men’s side, the big upset of day eight was Kei Nishikori defeating No. 6 Jo-Wilfried Tsonga 2-6, 6-2, 6-1, 3-6 and 6-3.

So what can we expect Tuesday on day nine?

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On the women’s side, the headliner is No. 1 Caroline Wozniacki vs. No. 11 Kim Clijsters. 

The world’s No. 1 has been unstoppable thus far, but now she meets the old, wily veteran who has all the experience in the world.

No. 3 Victoria Azarenka vs. No. 8 Agnieszka Radwanska will be the prelude match.

On the men’s side, the top match of day nine will be No. 11 Juan Martin Del Potro vs. No. 3 Roger Federer at the Rod Laver Arena. 

It will be, by far, the biggest test of Federer’s tournament, and will show us if the 30-year-old truly does have a shot to win another Grand Slam, or if those days are officially behind him.

The other quarterfinal match pits the resurgent No. 2 ranked Rafael Nadal against No. 7 Tomas Berdych, and is worth watching just to examine how Nadal is playing with his various ailments. 

Coverage begins at 7 p.m. EST on the Tennis Channel and continues from 9 p.m. to 2 a.m. and from 3:30 a.m. to 6 a.m. EST on ESPN2. 

DirecTV subscribers can also catch every match through the Australian Open Experience.

You can find a full schedule of Monday's matches below and at the official website of the Australian Open.