- Rafael Nadal is through to last eight after a routine win over Diego Schwartzman
- Nadal eased through the first set before inflicting more damage on his opponent
- He lost the second set in a tie-break but responded to win in four sets
- The one-time Australian Open champion takes on Marin Cilic in the next round
Rafael Nadal dropped his first set of the tournament but recovered to defeat Diego Schwartzman and ensure he will stay world No 1 after the Australian Open.
The top seed found himself in a real battle in the fourth round with diminutive Argentinian Schwartzman, who stands only 5ft 7in tall but packs a punch.
The 25-year-old is also a great fighter and recovered from a break down three times to take the second set before Nadal eventually ground out a 6-3, 6-7, 6-3, 6-3 victory after three hours and 51 minutes.
Rafael Nadal celebrates after sealing a four-set win over Diego Schwartzman on Sunday
The Spaniard ensured he will remain world No 1 after the Australian Open finishes
Reaching the quarter-finals means Roger Federer can no longer catch Nadal in the rankings this fortnight even if he successfully defends the title he won by defeating the Spaniard 12 months ago.
Federer is now the only man left in the tournament not to have dropped a set, and Nadal will be relieved to have survived this test.
He might well have won in straight sets yet also found his serve under near constant pressure, saving 15 of the 18 break points he faced.
The victory sent Nadal through to his 10th Australian Open quarter-final and 33rd overall at the slams, where he will face sixth seed Marin Cilic, who won his own tough battle 6-7, 6-3, 7-6, 7-6 against Pablo Carreno Busta.
Nadal unleashes one of his trademark forehands during his match on Sunday in Melbourne
Schwartzman clenches his fist after winning the second set of the match against Nadal