I didn't feel knee at all - Serena Williams

The world number one was under an injury cloud heading into the year's first grand slam, having suffered from knee inflammation at the Hopman Cup.

Williams, though, showed no signs of discomfort during a 6-4 7-5 win over Giorgi on Monday.

The American, 34, said she had no problems with her knee on Rod Laver Arena.

"It [the knee] is great," Williams said.

"It was an hour and 43 minutes and I didn't feel it at all."

Williams had tried to play at the Hopman Cup, but retired during her only match due to the knee worry.

While she said match practice would have been ideal, Williams feels her decision in Perth helped her.

"I would have never pulled out if I didn't need to, and it was just a last-minute decision. I even tried to play a match," she said.

"Obviously I wanted to play to get some match play."

As for her performance against Giorgi, Williams gave herself an "A for effort".

But her serve, which produced nine aces and was broken just once, pleased her most.

"I think I served well today. I think I got broken once, but other than that, I was able to stay focused on that part," Williams said.

"And I was able to serve really well and that really helped me."