Djokovic, Federer, Murray into Dubai semi-finals

The triple Grand Slam titleholder beat the seventh-seeded Tipsarevic 6-1, 7-6 (8/6) but only escaped from set point down at 5-6 in the tie-breaker thanks to a double fault from his fellow Davis Cup star from Serbia.

It raised hopes that Djokovic will on Friday witness another classic encounter with Murray, similar to their sensational five-hour Australian Open semi-final.

Murray reached the semi-finals with a 6-3, 7-5 victory Tomas Berdych.

Friday's other semi-final will see four-time Dubai champion Roger Federer, whose 6-3, 6-4 win over Mikhail Youzhny was his 12th over the Russian, against in-form Juan Martin del Potro.

The big Argentine defeated French fourth seed Jo-Wilfried Tsonga 7-6 (7/1), 6-2.

For a while Djokovic seemed likely to win comfortably against Tipsarevic, with whom he had "practised a million times."

He hit with great power off the ground, moved superbly, and won the first set in only 27 minutes.

But he ran into difficulty after failing to convert break points at 30-40 in the fifth and seventh games of the second sets.

Tipsarevic struck the ball more boldly, won many of the longer rallies with tenacious base-lining, and got the support of the crowd for his fight-back.

Djokovic, meanwhile, appeared to grow tense, and when he went 0-3 and 1-4 down in the tie-break a deciding set looked likely.

But after Tipsarevic's crucial double fault made it 6-6, Djokovic capitalised with a backhand slice to earn a second successive point against serve, and followed it with the winning combination of a good first serve and an unstoppable forehand follow-up.

Asked about playing Murray again, Djokovic said: "We are the same age and the first time we played each other was at the age of 11. So hopefully we will play another great match."

Murray progressed with a straight sets win over Berdych, the fierce-hitting fifth-seeded Czech against whom he had lost the previous three times.

The match ended in controversy as Berdych protested to Swedish umpire Mohamed Lahyani about a Hawkeye decision when he had a point to break back to six games all.

Murray's appeal to the computer replay showed that the line judge's call of fault to have been wrong and that his unreturned serve had in fact landed in.

When the Scot was duly awarded that point, Berdych argued that the rally should be replayed, claiming the line judge's call had interfered with his return of serve.

Television replays indicated however that the "out" call came after Berdych had struck his return, suggesting Lahyani's decision was the right one.

Murray went on to close the match out in that game, though it required six more rallies and seven match points altogether before he did so.

Later Berdych said he had been "shocked" by Lahyani's decision, adding: "If we look at all the rule books we going to see that if it's not a clear ace there is a repeat of point actually.

"I have no idea what Mohamed did. He is the best referee on tour and I never had anything like that with him."

Murray commented: "It's a bad rule, and one I have a big problem with. It comes down to kind of how the umpire sees it."

The other semi-final is between Grand Slam record-holder Federer and del Potro, the 2009 US Open finalist from Argentina whose victory against Tsonga was his second in five days.

Against Youzhny, Federer established breaks of serve early in both sets, and each time consolidated the advantage right through.

It suggested that the extra competition Federer has had this year - having included Rotterdam and the Davis Cup in his schedule - has made him satisfyingly match tight from the start of this week.

But Federer may feel hardly any more secure at avoiding another meeting with Tsonga by getting del Potro instead.

The Argentine's last victory over a top five player was against him.