Cilic will now face world No 1 Nadal in last eight of season's first grand slam in Melbourne
Australian Open Day 7: Dimitrov ousts Kyrgios to book place in quarter-finals alongside Nadal
Bulgaria's world No 3 Grigor Dimitrov won a gripping four-setter to knock Australia's big hope Nick Kyrgios out of the Australian Open on Sunday.
Dimitrov downed the 17th seeded Kyrgios 7-6, 7-6, 4-6, 7-6 in 3 hours, 26 minutes and will face Britain's Kyle Edmund in the quarter-finals on Tuesday.
Dimitrov stepped up his campaign after a couple of indifferent wins in the earlier rounds to avenge his defeat to Kyrgios in the semi-finals of this month's Brisbane International.
He won all three tiebreakers in a charged night match atmosphere on Rod Laver Arena before a capacity home crowd willing their player on.
"Playing against Nick is always tricky, two weeks I lost against him," Dimitrov said.
"He was serving and playing unbelievable and he fought really hard. It's one of those matches that you have to be locked in and try to get any opportunity you have.
"Even when I was serving for the match I felt that I was not finding my spots very well and I'm just glad I got through that match."
Kyrgios double-faulted to lose the opening set tiebreaker and was broken in the seventh game of the second set leaving the moody Australian to shake his head cussing at the changeover and uttering "embarrassing."
But he broke back with Dimitrov serving out for the set to bring up another tiebreaker.
It was the Bulgarian's greater poise and depth of shot that carried him through with Kyrgios frequently missing the lines.
The Australian broke early in the third set in his do-or-die bid to stay in the match and took the set with an ace.
But Dimitrov got a crucial service break in the eighth game of the fourth set when Kyrgios put a smash into the net to allow the Bulgarian to serve out for the match.
The unpredictable Australian managed to break back to force a third tiebreaker.
Again Dimitrov was too steady for Kyrgios, getting to three match points and winning it with a forehand pass.
Nadal secures place in Melbourne quarter-finals
Rafael Nadal battled through a huge test to make his 10th Australian Open quarter-final Sunday as Grigor Dimitrov ousted Nick Kyrgios to join him and Caroline Wozniacki kicked into full gear.
On an overcast and muggy day at Melbourne Park, the Spanish world number one was up against his most dangerous opponent yet in pocket-rocket Diego Schwartzman, one of the smallest men on tour.
The Argentine 24th seed endeared with his astonishingly powerful groundstrokes before Nadal prevailed 6-3, 6-7, 6-3, 6-3 in almost four hours on Rod Laver Arena.
It kept alive his push for a 17th Grand Slam title and also ensured he will remain number one when the new rankings come out after the tournament.
It was a great battle," said Nadal, who is chasing his second Melbourne title after beating Roger Federer in the 2009 final.
"Of course, I feel little bit tired, but I was able to keep fighting until the end."
He will play sixth seed Marin Cilic for a place in the semi-finals after the Croat beat Spanish 10th seed Pablo Correna Busta 6-7, 6-3, 7-6, 7-6.
The win was Cilic's 100th at a Grand Slam.
"I have played great tennis from the first round against tough opponents and now I am really looking to the next match, it will be definitely be a big challenge," he said of the Nadal clash.
Cilic set for Nadal showdown after major win No 100
Croatia's sixth seed Marin Cilic beat Spain's Pablo Carreno Busta in four sets to reach the quarter-finals on Sunday.
The former US Open champion downed the 10th seed 6-7, 6-3, 7-6, 7-6 and will face either Rafael Nadal of Diego Schwartzman in the quarters on Tuesday.
"There were lots of ups and downs and Pablo gave me a lot of trouble in that third set where he was twice a break up and it was difficult mentally," Cilic said.
"We had a lot of tough rallies in difficult humid conditions so I was really glad how I stayed in there mentally and really played well in the end."
Cilic served 20 aces, broke serve six times and made a total of 73 winners as well as winning the majority of the long rallies.
"That's my style of play. Pablo is extremely solid from the back of the court and has great shots both on the forehand and backhand and he was serving really good today," Cilic said.
"It was a big battle and I am really relieved that I played such a great tiebreaker at the end."
Australian Open Day 7: Caroline Wozniacki storms into last eight
Nadal and Dimitrov face tough tests: Matches to watch on Day 7
Edmund keeps British hopes alive
British hope Kyle Edmund reached his first grand slam quarter-final with a four-set win over Italy's Andreas Seppi on Sunday.
The unseeded Edmund, ranked 49, lost the opening set, but finished strongly to win 6-7, 7-5, 6-2, 6-3 and will face Nick Kyrgios or Grigor Dimitrov in the last eight.