Defending champion Andy Murray was handed a berth in the final of the Brisbane International on Saturday when Japan's Kei Nishikori retired from their semi-final with a knee injury.

Murray had taken the first set 6-4 and was up 2-0 in the second when Nishikori, who had treatment on his knee at the end of the first set, decided he couldn't continue and conceded the match.

The 25-year-old Murray will now play Grigor Dimitrov in Sunday's final after the rising Bulgarian star edged out Cyprus's Marcos Baghdatis 6-3, 5-7, 7-6 (7/5) in the first semi.

Nishikori started brilliantly against Murray and leapt out to a 4-1 lead before the reigning US Open champion began to find his range.

He quickly broke back then took control as Nishikori struggled with his movement around the court.

"I didn't know he was injured until late in the set," Murray said. "He was trying to play aggressively and keep the points short.

"When I made him play the ball more I had him in trouble."

Murray said he was relatively pleased at how he was playing a week out from the first Grand Slam of the year.

"I'm playing okay, a bit up and down," he said. "I served pretty well for the majority of the tournament.

"I've moved better every single match. Returning could have been better and my groundstrokes, I think with more matches, I'll start to hit them cleaner.

"When I've come up to the net I've volleyed relatively well... there is stuff for me to work on."

Dimitrov progressed after a thrilling win over 2006 Australian Open runner-up Baghdatis.

The young Bulgarian has been in superb form this week and looked on track for another convincing win after dominating the first set and going up an early break in the second.

But Baghdatis has always performed well in Australia and he began to trouble Dimitrov, putting enormous pressure on his opponent's serve with his aggressive returning.

Dimitrov's serve dropped off as Baghdatis raised his game and there was nothing between the two men as the third set went to a tiebreak.

Dimitrov got the early break at 4-2 when Baghdatis became unsettled by a time violation, only for the Cypriot to storm back and level proceedings at 5-5.

However, the 21-year-old Dimitrov won the next two points to make his first final on the ATP tour.

"I think it will be a fun match for me (against Murray), I have nothing to lose tomorrow," Dimitrov said.

"I just want to go out there and compose myself and say, 'Okay, it's your first final, don't be nervous at least'.

"I think it's going to be a good match."