"I'm playing good tennis. I'm confident that I think it needs a good performance by my opponent probably to beat me," Federer, who opens his title defence against Uzbekistan's Denis Istomin on Monday, told a press appearance.
The Swiss said he was aware of the potential of Istomin, who upset defending champion Novak Djokovic in Melbourne in 2017.
"I know what Denis did to Novak. I watched basically the entire game a couple of years ago when he beat Novak here. I've had some tough ones against him in the past. He can play well on fast courts, and that's what it's going to be a little bit here as well," added the world number three, who has won all of his six previous matches against Istomin.
Federer, who starts his 20th Australian Open campaign on Monday, has won the title six times, including its last two editions.