Russian fifth-seed Andrey Rublev has saved two match points to clinch an Australian Open quarterfinal spot with a tense five-set win over Danish teenager Holger Rune.

Rublev staged a stunning fightback in a super tie-break to secure a a 6-3, 3-6, 6-3, 4-6, 7-6 (11/9) win with a dead net cord winner on his third match point against ninth-seed Rune.

At the end of five gripping sets, Rune raced to a 5-0 lead in the tie-break and was also up 7-3 before suffering a dramatic collapse.

Rublev snatched victory when his backhand return hit the net tape and fell over to send 19-year-old Rune crashing out of the tournament.

The result — after three hours and 37 minutes on court — sets up a blockbuster quarterfinal clash with nine-time champion Novak Djokovic, who dispensed of Australian hope Alex de Minaur 6-2, 6-1, 6-2.

"I never was able to win matches like this," Rublev said in his on-court interview.

"Especially in very special tournament like Australian Open, to be in quarterfinal is something that I will remember, for sure, all my life.

"I have no words, man. I'm shaking."

Rublev was twice up a set — only to be pegged back — and was 5-2 down in the fifth set.

He saved two match points to send the fifth set to the super tie-breaker and won eight of the last 10 points to seal victory.

Young American Ben Shelton also advanced to the last eight via a five-set win, having been taken the distance by his countryman JJ Wolf.

Both players were unseeded in Melbourne, with Shelton winning 6-7 (5/7), 6-2, 6-7 (4/7), 7-6 (7/4), 6-2 after three hours and 47 minutes at the John Cain Arena.

Shelton — who ended Australian Alexei Popyrin's tournament in the third round — is contesting just his second major.

In the quarterfinals, the 20-year-old plays fellow American Tommy Paul, who defeated 24th-seeded Spaniard Roberto Agut Bautista 6-2, 4-6, 6-2, 7-5.

AAP/ABC