Angry Nalbandian blasts referee after Isner loss

A furious David Nalbandian blasted the chair umpire for over-ruling a point and denying him a Hawk-eye challenge towards the end of his marathon 4-6, 6-3, 2-6, 7-6, 10-8 loss to American John Isner in the second round of the Australian Open on Wednesday.

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Holding a break-point at 8-8 in the fifth set, Nalbandian was left fuming after Frenchman Kader Nouni over-ruled a first serve by Isner as an ace after it was called a fault.

The Argentine walked up to inspect the mark where the ball had bounced and demanded a challenge but was denied by Nouni who ruled he had not made it quickly enough.

There is no set time that players are bound by to mount challenges and it is up to the umpire's discretion.

A non-plussed Nalbandian remonstrated with Nouni for some minutes as boos and jeering rang out in the stands at Margaret Court Arena, before he grudgingly returned to the baseline with the score at deuce.

Isner held serve to lead 9-8 and subsequently broke his opponent in the next game to seal the four-hour and 41-minute match in the gloaming, thumping his chest in triumph to the delight of the packed crowd.

Nalbandian told reporters he thought Nouni was not qualified to umpire.

"I called Hawk-eye and he didn't give it. I never seen something like that," the 2002 Wimbledon finalist said.

"There (was) no time to call ... I don't think he's able to do these kinds of matches ... Absolutely no doubt."

Isner's win was a timely reminder of his marathon man credentials. The American fought a record 11-hour epic with Frenchman Nicolas Mahut at Wimbledon in 2010.

"The sun going down helped me a lot here," Isner, who will play Spanish 18th-seed Feliciano Lopez in the next round, said in a courtside interview.

"The temperature dropped and it wasn't that hot.

"I was cramping a bit in my right leg. But somehow I pulled it out," he added.