Serena Williams retired hurt from her Hopman Cup match against Jarmila Wolfe on Tuesday (5th January) in Perth, Australia.

Lleyton Hewitt defeated Jack Sock 7-5, 6-4 to give Australia Gold victory over the USA at the Hopman Cup in Perth on Tuesday (5th January).

Having missed Monday's opening rubber of the Hopman Cup, Serena Williams was looking to set Team USA on the right track.

Serena here firing a forehand past Australia's Jarmila Wolfe to lead early on.

Although Wolfe stayed in the game and held firm defensively to hold her own service game and level up the match.

Wolfe would take the first set before Serena's injury issues flared up again.

Although the World No.1 saying her inflamed knee would in no way prevent her defence of the Australian Open.

"I definitely think I will be able to get it right for Australia. And I'm literally taking it one day at a time, and, you know, I just have so much going for me right now and I just only think positive and I know I'll be okay. So, it's just not even a bump, it's just really a minor thing in the road at the minute... fly over it and keep going."

That meant that Australia Gold led the round robin with the USA before the men's clash of young versus old.

Lleyton Hewitt preparing for his last ever Australian Open served up a typically gritty performance against World No.24 Jack Sock.

7-5 in the first as his partner in the doubles to follow Wolfe watched on, before another attritional set saw the 34-year-old Aussie clinch the tie for the hosts.

The doubles was already deemed a walkover with Serena pulling out, yet that didn't stop Hewitt and Wolfe finishing off the tie in straight sets.

Australia now need a win dominant win over the Ukraine to make the final on Saturday.