Spanish second seed Rafael Nadal is through to the quarter-finals of the Australian Open after his French opponent Paul-Henri Mathieu retired injured from their match.

Nadal was in control, leading 6-4 3-0, when Mathieu told the chair umpire at the change of ends, that he could not continue.

Nadal will play Finnish 24th seed Jarkko Nieminen in the quarter-finals.

Nadal said he was happy with the way he had been playing, but it was a sad way to progress in the tournament.

"I'm sorry for him, I know it's a very tough moment for him," he said.

"I've had it happen sometimes the same, it's a very tough moment so I'm sorry for him.

"I'm happy to be through to the quarter-finals, not like this, but I'm very happy anyway." Mathieu, who has never been past the fourth round of a grand slam tournament, cited a strain in his left calf muscle as the reason he could not continue.

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