Gallery: The best pictures from an action-packed day four at the Australian Open

Third-round action continued at the Australian Open with Novak Djokovic, Alexander Zverev, Serena Williams and Simona Halep all in action at Melbourne Park.

Enter Kei Nishikori.

Go on, guess who it is.

The above picture was Nishikori as well, but onto a pumped up Elina Svitolina.

Blowing kisses after her win over Viktoria Kuzmova.

World number one Simona Halep had to dig deep to come through her second round match. Very deep.

From behind the lens.

A Stan Wawrinka backhand.

And then it rained and the ball kids had to do some mopping up.

Serena Williams was in action, and she was certainly enjoying herself.

Alexander Zverev looked nervy from the off, though, even with himself cheering him onto court.

The face of a man who’s had to deal with Novak Djokovic’s brilliant defence for two hours…

Certainly, the world number one seemed to be managing to reach pretty much everything!

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