(CNN) -- Defending champion Novak Djokovic of Serbia advanced to the fourth round of the Australian Open on Friday but only after a tough four-set workout against Amer Delic.
Novak Djokovic: "I need some matches like this to feel really what is Grand Slam all about."
Djokovic, the No. 3 seed, was kept on court for more than three hours by his 127th-ranked opponent before finally wrapping up a 6-2 4-6 6-3 7-6(4) victory in a fourth set tiebreak.
The battling Delic, a Bosnian-born American who only qualified for the main event following Nicolas Kiefer's withdrawal from injury and had already played 10 sets on his way to round three, refused to be dominated by Djokovic.
He fired down 16 aces and 46 winners, won the second set in impressive fashion and had two set point opportunities to take the match to a deciding set in the fourth.
"I need some matches like this to feel really what is Grand Slam all about," said an appreciative Djokovic, who next faces either Mardy Fish or former finalist Marcos Baghdatis.
"It's about those long four, five set matches on the heat like this. I didn't really plan to be that long on the court. You always want to finish the job as soon as possible. The positive thing is that I got more time out there, and [I'm] looking forward to the upcoming match."
American No. 7 seed Andy Roddick also advanced Friday with a 6-3 6-4 6-2 win over veteran Spaniard Fabrice Santoro, while the big match of the day sees No. 2 seed Roger Federer face Marat Safin, the 2005 champion and a perennial crowd favorite in Melbourne.
Safin's younger sister, No. 3 seed Dinara Safina, is already through to round four in the women's singles, following a 6-2 6-2 win over Estonian Kaia Kanepi.
Serbian top seed Jelena Jankovic also made comfortable progress with a 6-4 6-4 win over Japan's Ai Sugiyama.