Bulgarian Grigor Dimitrov held his nerve to knock home favourite Nick Kyrgios out of the Australian Open in a fourth-round thriller at the Rod Laver Arena on Sunday.

Third seed Dimitrov absorbed 76 winners and struck 64 of his own to prevail 7-6(3) 7-6(4) 4-6 7-6(4) and set up a quarter-final with unseeded Briton Kyle Edmund who beat Italian Andreas Seppi 6-7(4) 7-5 6-2 6-3.

Top seed Rafa Nadal was rattled by a feisty challenge from Diego Schwartzman but fought back strongly to move past the diminutive Argentine 6-3 6-7(4) 6-3 6-3.

The 16-times grand slam champion, who was broken three times as he lost the third set, responded with grit to claim the win on the third match point with a rocketed backhand return.

Victory ensured that Nadal will retain his world number one ranking as he set up a meeting with sixth seed and former U.S. Open champion Marin Cilic for a place in the semi-finals.

Cilic earlier ground down Spaniard Pablo Carreno Busta 6-7(2) 6-3 7-6(0) 7-6(3) at the Margaret Court Arena.

Second seed Caroline Wozniacki needed a shade over an hour to thrash Slovakia's Magdalena Rybarikova 6-3 6-0 and advance to the quarter-finals. The Dane next meets Carla Suarez Navarro who beat Estonian Anett Kontaveit 4-6 6-4 8-6.

Belgium's Elise Mertens progressed to her maiden grand slam quarter-finals in her first appearance in the Australian Open main draw, beating Croatian Petra Martic 7-6(5) 7-5.

Her opponent in the next round, Ukraine's Elina Svitolina, firmed as a strong contender for the title with a flawless 6-3 6-0 victory over Czech qualifier Denisa Allertova in the early hours of Monday morning.