Merciless Medvedev moves into last eight in Melbourne

The fourth-seeded Russian won his first career five-set match in the third round but there was no need for a prolonged spell in the sun to see off McDonald on Margaret Court Arena.

Daniil Medvedev firmed as an Australian Open contender when he brushed aside Mackenzie McDonald 6-4 6-2 6-3 to reach the quarter-finals and extend his winning streak to 18 matches on Monday.

Russia's Daniil Medvedev hits a backhand to United States' Mackenzie McDonald during their fourth-round match at the Australian Open tennis championships in Melbourne, (AP)

The fourth-seeded Russian won his first career five-set match in the third round but there was no need for a prolonged spell in the sun to see off McDonald on Margaret Court Arena.

World number 192 McDonald had some luck going to the net but could not match the power of Medvedev's serve or the intensity the Russian brought to bear on big points.

Medvedev converted six of the seven break points he carved out, the last to win the match and set up a last-eight clash with compatriot Andrey Rublev or Norwegian Casper Ruud.