Australian Open - Men: Nadal off after injury

Andy Murray reaches last four as injury forces Nadal to quit. Marin Cilic beats Andy Roddick in five sets.

Murray was 6-3 7-6 (7-2) 3-0 up when a right-knee injury forced Nadal to quit.

The British number one took a tense first set in 53 minutes and fought back from 4-2 down in the second, eventually running away with the tie-break.

Nadal battled on after having treatment on his knee at the start of the third set, but could not continue for long.

It was a sad end to an absorbing encounter but the end result is that Murray is through to the last four for the first time in Melbourne, where he will meet 14th seed Marin Cilic.

Murray regretted the eventual manner of his victory but was more than satisfied with the level of his performance, and feels it bodes well with his rematch with Cilic, who beat him in the 2009 US Open.

"I've known Rafa since I was 13 or 14 and he is someone I always looked up to when I came up through the juniors," Murray said afterwards. "He is my favourite player to watch with his energy and I am a bit gutted for him.

"I had to come through a few tough moments at the start of the match when I was going for it a bit too much but I played really well.

"I had to go for my shots and play big tennis and when the big points come you have got to try to keep them short. You do not want to play long points against Rafa - I served and volleyed a little bit and everything went well."

Croatian Marin Cilic was forced survive a late fightback from Andy Roddick before booking his place in the last four of the Australian Open.

The Croatian 14th seed was on course for a comfortable win at two sets up as Roddick struggled to cope with a shoulder problem.

But the American seventh seed hit back to force a decider, only for Cilic to seal a 7-6 (7-4) 6-3 3-6 2-6 6-3 win.

"It wasn't easy. I got experience of it during the week," said Cilic following his third five-set win of the tournament.

"I just had a few extra gears in the last set. It wasn't easy when he started to play a lot better.

"I really struggled on my serve and he put a lot of pressure on me and I didn't know what to do.

"But I just took it point-by-point... and then I got the break."

Roddick admitted the injury had been causing him problems before the match, and had prevented him having "the full deal" against Cilic.

"I felt it a little bit the other night, the cold weather, trying to hit through those for a little while. I didn't hit yesterday," he said afterwards.

"Felt pretty good today in warm-up, the first couple games, then I think I aggravated something.

"The trainer said it was stemming from the neck down. By the end of the first set, I was pretty numb in the bottom two fingers.

"I could still hit it pretty hard, I was just having trouble controlling it. I didn't really have full deal."