Nadal downs Nishikori

Melbourne - World number one Rafael Nadal fought off a spirited challenge from Japan's Kei Nishikori to win through to the quarter-finals of the Australian Open on Monday.

The Spaniard won 7-6 (7/3), 7-5, 7-6 (7/3) in three hours 17 minutes and will play Bulgaria's Grigor Dimitrov in the last eight.

Nishikori, under new coach Michael Chang, pressed Nadal all the way and had his chances to take sets off the top seed only to fall down on forehand errors.

Nadal was angered when he was called for a time violation by chair umpire Eva Asderaki at deuce while 4-4 at a critical time in the third set, but he regathered his composure to win the match in his second tiebreaker.

The 13-time Grand Slam champion's renowned fighting qualities came to the fore when he won the big points for his sixth win over Nishikori.

"He's a fantastic player and Kei is able to hit the ball very early and the ball was coming back very quick," said Nadal, who is now on a nine-match winning streak.

"It was difficult for me to take position inside the court and I was close to losing every set so I congratulate Kei and I feel he will have a great season.

"He is always very quick around the court, but today with his backhand today he was able to take the ball quicker and that's why I was struggling for my position on the court."

Nadal broke Nishikori's opening service but that was only a precursor to a tremendous opening set by the Japanese star.

He broke the world number one's serve for the first time in the tournament and more than matched Nadal with his shot-making and speed around the court.

The set went to a tiebreaker but Nadal wrapped it up on his second set point in one hour and five minutes.

Nishikori again broke the struggling top seed who missed with a forehand in the fifth game of the second set.

But Nadal got the break back in the eighth before there was a delay as he sought a replacement shoelace after it snapped during a rally.

The set looked headed for another tiebreak before Nadal broke Nishikori in the 12th game with a forehand to take a two sets to love advantage.

Nadal broke early in the final set and fought off two break points in his next service game only to hit a double fault on break point to drop service in the seventh game.

Nadal was broken for 5-4 and was upset when he was called for a time violation in between points by the chair umpire, but Nishikori was broken back as he served for the set.

Once again Nadal's nerve and skill held strong in the tiebreak to take the match and advance to the last eight.