Not even Denis Istomin can believe that he beat Novak Djokovic

The upset of six-time Australian Open champion Novak Djokovic in Melbourne has given Denis Istomin new confidence in his ability.

The 117th-ranked wild card defeated the reigning champion in five sets for the biggest win of his career.

"I feel I can play with these guys, and to be with them on the same level,” the Uzbekistani said in his on-court interview after the match.

Before the tournament, he would have scoffed at the idea that he could keep up with Djokovic for more than four-and-a-half hours—and come away the winner.

"I would say, 'Are you crazy or what?’” he told reporters. "Especially in five sets, for sure. For me, [it] was impossible to think about [going] five sets with Novak, physically and mentally."

The former world No. 33 had to win the Asian wild-card playoffs just to get into the tournament—he had to save match points along the way—having fallen in the rankings because of injury.

"It was a good, good thing that I can play this tournament and get [a] wild card,” Istomin said. “Now I'm in [the] third round. So thanks, Australia, to organize this tournament.”

It was only the second Top 10 win of Istomin’s career. He’ll play Pablo Carreno Busta in the third round.