The contrast between the players could could hardly be more stark.

Even at the age of 34, and facing ongoing knee problems, Williams still looks unbeatable.

In an exhibition of power-hitting and unplayable serves, the world number 1 looked as competitive and passionate as ever.

Russian Daria Kasatkina is just 18 years old and is ranked number 69 in the world.

She made the third round in last year's US open, and despite the 6-1, 6-1 loss to Williams, this equalled her best grand slam outing.

While Williams looked typically calm and focussed as she walked onto Rod Laver Arena, Kasatkina seemed overawed by the occasion.

The Russian served up multiple double-faults in the first game, mistakes one can hardly afford to make when facing the best woman player in the world.

The crowd cheered when she managed to win her first game, but Williams hit back with a near-perfect service game in which Kasatkina didn't manage a single point.

This was the first time Kasatkina and Williams played, but it may not be their last.

After the match, Williams could be heard praising her opponent as they shook hands at the net.

"I love your game, great forehand," she said.

Next time the younger woman will be a little older, with more match experience, and may prove a greater challenge to the queen of world tennis.