Roger Federer knew something had to change.

In the space of 64 minutes he had thrown away a two-sets-to-love lead and was staring defeat in the face.

At 35, grand slam semi-finals don’t come around as often as they used to, and for all Federer knew, this might have been his last.

So, thrown by Stanislas Wawrinka’s injury-induced go-for-everything attitude that completely turned Thursday’s match on its head, Federer did something he very rarely does – called for an off-court medical timeout.

He later claimed, in a cagey post-match interview with the Seven Network’s Jim Courier, that he was hampered by “a leg thing” and praised the ATP physio for his “magic hands”.

It was far from convincing, nor was Federer’s eventual 7-5 6-3 1-6 4-6 6-3 triumph against his compatriot, but the fans barely cared as their dream of a final between the Swiss maestro and Rafael Nadal – who plays Grigor Dimitrov in Friday’s other semi-final – remained alive, just.

Federer shed further light on his timeout in his post-match press conference, saying: “I think these injury timeouts, I think they’re more mental than anything else.

“For the first time maybe during a match you can actually talk to someone, even if it’s just a physio. We know him well.

“It maybe relaxed Stan, you know, just to be able to talk about I don’t know what. The same thing for me, as well.

“I only really did take the timeout because I thought, ‘He took one already, maybe I can take one for a change’, because I’m not a believer in any way that we should be allowed to take a lot of timeouts.

“People know I don’t abuse the system. I hope it’s going to stay that way in the future for me, too.”

Wawrinka had indeed called for the trainer following a second set in which he broke his racquet in two pieces over his leg in sheer frustration, as even his best shot – his one-handed backhand – let him down.

Wawrinka hits a backhand return. Photo: AP

He looked defeated when he returned to Rod Laver Arena sporting strapping on his right knee, but with Federer, there were no signs of his treatment.

While Wawrinka’s knee was strapped tight, crucially, his mind was free.

It seems crazy to suggest someone playing in the last four of a grand slam had nothing to lose, but Wawrinka played like it, ramping up his aggression, both with his service speed and his return.

Perhaps Federer, just for a moment, started to think about Sunday’s final, but it can’t have lasted long, such was Wawrinka’s dominance in a 26-minute third set in which, at one stage, he won 20 of a possible 26 points.

The first game of the fourth set told the story, as Federer not only framed a ball out of court, but double-faulted, before, facing a break point, he rushed to the net.

Wawrinka, who won the title at Melbourne Park in 2014, passed him with that backhand, a shot that deserved a noisy reaction from the crowd, particularly to earn a break, but was met with stunned silence.

This just wasn’t meant to happen.

Federer broke back in the next game and Wawrinka’s plight was shown when, unable to stop himself suddenly, he jogged into the tunnel following a point.

Games remained on serve until, at 4-4, Wawrinka earned himself three break points. Federer saved two, but had no answers for a fiercely hit forehand on the third, and before long, the eventual winner was calling for the trainer.

A delay of eight minutes followed, but to his credit, Wawrinka’s mindset did not change.

Federer becomes the oldest man to reach a grand slam final since Aussie Ken Rosewall in 1974. Photo: Getty

The first four sets were a tale of two halves and not the epic some expected, but the start of the fifth set was gripping, as Federer rose to his opponent’s level.

In two separate games, Federer saved break points, but, serving at 2-3, by his own admission, Wawrinka “did a really bad game”.

It was capped off by a double-fault to give Federer the break, something rarely cheered by a tennis crowd, let alone roared.

But this Australian Open is different. It is all about the fairytale.

Federer – who has 17 grand slam titles to his name, the last coming at Wimbledon in 2012 – closed it out from there, but did so knowing he had survived a major scare.

Debate is sure to rage on the ethics of his timeout and it is a move he may not have pulled in his prime.

Federer knows the end is near, though. And he is desperate for at least one more grand slam.

He is now just one match away.