Cilic, a semi-finalist here last year, was well beaten long before he netted a return after two-and-a-half hours and a delighted Nadal moved on with a snarl to a quarter-final against fellow Spaniard David Ferrer.
"Today I felt very good, no?" he said. "I didn't sweat like the other days. So that's fantastic news for me. The better news is I played much better than the rest of the days.
"I was able to play with high intensity, very good rhythm, playing more inside the court. So play more aggressive, changing rhythms with the slice and with the topspin, backhand."
Losing finalist here last year, British fifth seed Murray had conceded just 16 games in three matches to reach the fourth round and was equally parsimonious in dispatching Austrian Juergen Melzer 6-3 6-1 6-1.In Image: Rafael Nadal of Spain signs autographs for fans after beating Marin Cilic of Croatia during their fourth round match at the Australian Open tennis championships in Melbourne, Australia, Monday, Jan. 24, 2011.Full Coverage: Australian Open 2011