Rafael Nadal has said that his knee is "much better" after cruising into the third round of the Australian Open.

The Spaniard revealed that he was in "unbelievable pain" on the eve of the tournament when he heard a crack in his right knee.

"It is much better and I am so happy the knee is improving and I am able to play without pain," he said after his 6-4 6-3 6-4 victory over Tommy Haas.

Nadal also praised his 33-year-old opponent.

"He's a fantastic player. He's had a lot of injuries the last couple of years but it's always great to play Tommy," he said.

"He's thinking about retiring but I thought he played well this afternoon."

Nadal took the Australian Open title in 2009.