Uzbek Denis Istomin pulled off an Australian Open upset for the ages when he sent reigning champion Novak Djokovic tumbling out of the year's first grand slam in a near five-hour epic on Thursday.

The 30-year-old world number 117 played the match of his life to hand the six-times champion only his second defeat in seven years at Melbourne Park with a 7-6(8) 5-7 2-6 7-6(5) 6-4 second-round win on Rod Laver Arena.

Source: b'Reuters'

Istomin let out a huge roar of delight when he ensured Djokovic's earliest exit from the tournament in more than a decade, the 12-times grand slam champion sending a service return long to end the contest after four hours and 50 minutes.

"First of all I feel sorry for Novak. I was playing so good today," Istomin said on court.

"I mean, I surprised myself also today. I want to thank my team ... who do a good job. Amazing. So much emotion on my mind so I cannot hold it you know but I want to say thanks very much for coming to support me."

Source: b'Reuters'

The wildcard, who hit 63 winners, edged the first set but simply refused to fold when second seed Djokovic hit back to win the second and third sets.

Clinching the fourth on another tiebreaker to send the match into a decider, Istomin grabbed an early break in the fifth and held his nerve to deliver a famous victory.

"I mean it was tough, since third set I get cramping in my leg so I don't know how I hold it," he added. "But I was physically normal today."

After the biggest win of his career, Istomin moves onto a third-round meeting with Spaniard Pablo Carreno Busta.