Andy Murray [Images] knows what he must do to stretch his winning streak over 13-times grand slam champion Roger Federer [Images] -- the Swiss, though, is still unsure how to stop his nemesis.

World number two Roger Federer has lost to the Scot five times in seven career meetings, including their last three encounters, and next meets him in the semi-finals of the ATP event at Indian Wells.

"He's a great player and great players are tough to play against. He's young, so you still have to figure him out a little bit. He's changing his game as time goes by. Every time you play him, he plays a bit different," 27-year-old Federer said.

"Whereas for me, it's different. He knows what to expect. That's the advantage of a youngster. There are disadvantages in that they're a bit more inconsistent but he's been very consistent, at a young age, which is impressive to see."

Although Murray has the advantage in their head-to-head record, Federer believes he has the edge on the bigger stages.

"I'm aware he has beaten me more than I've beaten him but, on big occasions, I think I came through," Federer told reporters after battling past Spaniard Fernando Verdasco 6-3 7-6 on Thursday.

"I have to build on that and make sure I play a tough and good match against him. Anything else is not going to do the job."

Federer, playing in his first event since being sidelined by a back injury after losing last month's Australian Open [Images] final to Rafa Nadal, beat Murray in straight sets in the U.S. Open final in September.

Since then, however, he has lost to the Scot in Madrid, Shanghai and Doha.

"Every time I won the first set, he kind of got stronger and stronger as the match went on," Federer said. "I've just got to make sure I finish because I know it's not physical, the end of the matches.

"Three sets, it never really becomes physical. It's only maybe in the fifth set if that that were to happen."

Asked if he had unfinished business to resolve against Murray, Federer replied: "Not really."

World number four Murray, who beat Federer 6-7 6-2 6-2 in the Qatar Open semi-finals in January when they last met, is looking forward to their next encounter at Indian Wells.

"We know each others' games pretty well," the 21-year-old said after a hard-fought 7-5 7-6 victory over Croat Ivan Ljubicic.

"If I want to beat him, I need to play one of my best matches.

"It's important to serve solid, make a lot of balls and not feel like you have to do anything special on each point to win against him."

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