World No 4 Andy Murray wasted six match points and overcame a knee injury to beat Tomas Berdych 6-3, 7-5 in the Dubai Tennis Championships quarter-finals on Thursday, while Roger Federer also made it through to the last four.
"I had a problem with it (the knee) since Brisbane and it's come and gone," Murray told reporters after a match played in searing desert heat.
"It was a bit sore right before the tournament. I didn't feel it at all in the first couple of matches, and then right at the beginning of the second set I felt it.
"It's not something that stops me sort of running around. I want to try and get rid of it, because there are a lot of the big events coming up."
Murray, who went into the match with a 3-1 losing record to Berdych, appeared to be cruising at one set up and 2-0 ahead in the second, but he double-faulted to gift the Czech a break back for 2-2.
The Briton's movement was increasingly laboured but his reply was immediate, breaking again, only for Berdych to do the same and level at 3-3.
The Czech was on top and looked as though he could square the match, but Murray dug in and broke once more, playing a forehand cross-court shot from wide of the tramlines that Berdych had no reply to for a 6-5 lead.
Murray, 24, wasted six match points on serve. The first three were backhands into the net and a fourth an errant forehand drive but he eventually triumphed when Berdych put a forehand long.
"In my whole career on the tour, I think I've only lost one match where I served for it, two maximum," said Murray.
"I played three great serves to bring it to 40-love and then missed a few first serves in a row and he went for some big shots," he added.
"Once you're back at deuce you're thinking, God, I've just blown three match points. So you kind of just want to try to get through it if you can. I went too defensive. I went too far behind the baseline and was letting him dictate points."
Murray's solitary defeat in 2012 came in a five-set epic against Novak Djokovic in the Australian Open semi-finals and he will meet the Serb in the last-four in Dubai should the world number one overcome compatriot Janko Tipsarevic later on Thursday.
World No 3 Federer will play either Argentine Juan Martin Del Potro or France's Jo-Wilfried Tsonga in Friday's other semi-final after defeating Russia's Mikhail Youzhny 6-3 6-4 as dusk set in.
Federer had won all their 11 previous meetings stretching back 12 years and Youzhny, 29, never looked like ending his losing streak after slumping to 3-1 down in the first set.
Federer, 30, saw out the first set with a fierce serve the ailing Youzhny could only club long.
The Russian, who has dropped to 34th in the world from a career-high eighth, played another poor forehand to lose his serve on the opening game of the second set, effectively ending the contest as Federer -- a 16-times Grand Slam winner -- served out.
The Swiss has yet to drop a set in the opening three rounds in Dubai.
"The surface speed is helping and I have a good focus this week," Federer said in a court-side interview.