It was hard at times to recognise the Roger Federer who soared, dipped and soared like a wounded eagle against Kei Nishikori for more than two hours here

as the same player who was so imperious beating the world number one Novak Djokovic in straight sets on Tuesday.

Perhaps it was the beard – which Federer revealed has taken him a week to grow to grey stubble level – or, more seriously, Nishikori, who finally came to life in the tournament.

“The good thing is that I am through to the semis,” said the Swiss. “It relaxes your nerves. I’ve been in this position before, so I know how to handle it.”

It was, however, a curiously disjointed performance by Federer, who led 3-1 before edging the first set, blew a 4-1 lead in the second when a routine win was his for the taking and led 4-1 again in the concluding set before allowing Nishikori back into the fight for a third time, then rediscovered his rhythm to win 7-5, 4-6, 6-4.

It was one of the tournament's better struggles and, for more than a few moments here and there, Nishikori, attacking Federer's second serve with force, held real hopes of fashioning an unlikely passage into the semi-finals. He needed to beat Federer, obviously, having lost to Djokovic, while hoping against hope that Tomas Berdych could later beat the Serb for only the third time in 23 attempts. All the mathematical juggling in the world, however, could not disguise Nishikori's failure to capitalise on so many great chances.

Break points

He had twice as many break points, 12, as Federer, but converted only five, while his opponent nailed each of his six opportunities – and just as well he did, because he might easily have lost this match.

As well as hitting some dazzling winners, most of them from positions of considerable peril, Federer threw in a couple of untamed howlers among his 35 unforced errors, none more embarrassing than a forehand at the net towards the end of the second set that nearly hit the crowd on the full.

Federer’s work at close quarters was not as precise as when he was subduing Djokovic earlier in the week; nor will he be satisfied with his serve, scraping together only 54 per cent on first attempt. Yet he found a way, as he does so often. It was not Federer at his scintillating best but it was a rough-hewn win, one suited to his unshaven look.

Federer's old adversary, Rafael Nadal, is the only other player in the tournament with a 100 per cent winning record and the Spaniard will be determined to keep it that way against his compatriot David Ferrer on Friday. If Nadal wins to top Group Ilie Nastase, he will play Djokovic in one semi-final, while Federer will play either Andy Murray or Stan Wawrinka in the other. Guardian Service