Melbourne, Jan 24 (IANS): World number one Rafael Nadal was forced to retire hurt in his quarterfinal match with Croatia's Marin Cilic at the Australian Open on Tuesday.

After hitting the ball well and looking in top form, the Spaniard's injury came as a huge disappointed to tennis fans, reports Xinhua news agency.

Up in the first set and looking in control against Cilic, it didn't take long for the tournament's sixth seed to strike back.

The Croatian found another gear and brought the score to a set a piece.

The tension continued with the third set finishing in a tie break and although Nadal edged ahead. At the beginning of the fourth set it was visibly evident that the 13-time Grand Slam winner was in severe pain.

Clutching at his upper leg and hip area, Nadal bravely battled on in the fourth but lost the set 6-2.

At two games down in the fifth and three hours and 47 minutes into the match, Nadal told the umpire he could not continue.

The final score officially ended 3-6, 6-3, 7-6 (7-5), 6-2, 2-0.

"I started to feel the muscle little bit tired in the third, but playing normal," Nadal explained.

"Then in the fourth at one movement, one dropshot I think, I felt something and at that moment I thought something had happened, but I didn't realize how bad it was in that moment.

"It is not the first time an opportunity has gone for me but I am a positive person, and I can be positive, but today is an opportunity lost to be in the semifinals of a Grand Slam and fight for an important title for me. It's a tough moment," he added.

In another shock result, Kyle Edmund from Britain overcame world number three Grigor Dimitrov in four sets, booking his place in the semifinals for the first time in his career.

The win will see him face off against Cilic on Thursday for a place in the final.

In the women's bracket, the surprises continued when 22-year-old Belgium player Elise Mertens knocked out world number four Elina Svitolina in straight sets.

However, there was no such trouble for world number two Caroline Wozniacki, she blasted her way to the final four by downing Spain's Carla Suarez Navarro in a spirited contest that ended 0-6, 7-6 (7-3), 2-6.

"I was disappointed I didn' t close it out in the second set," Wozniacki said. "But I managed to stay composed and finish it in the third, so I'm excited about the semifinals."

The Danish hitter will now face Mertens on Thursday in the semifinals.