Jack Draper’s transformation from tennis sick note to iron man of Melbourne Park has been inspired by an unexpected ally: a breathing coach, who is encouraging him to use his nose rather than his mouth.

Ever since his very first appearance on the ATP Tour, when he collapsed on the court in Miami and was forced to retire, Draper has been sensitive to heat and stress.

Two years ago, in the first round of the Australian Open, he was setting a rusty Rafael Nadal all sorts of problems until he started cramping early in the third set. Then, at this same tournament last season, he vomited in a bin after scoring a maiden five-set win over the USA’s Marcos Giron.

But this tournament has been very different. Despite having come into the event with no matchplay behind him, because of a hip issue that disrupted his off-season, Draper has fought back from two sets to one down in three consecutive matches without needing so much as a medical time-out.

He has spent just over 12½ hours on the match court already, five hours more than his next opponent Carlos Alcaraz (whom he is due to face at 4.30am GMT on Sunday morning). And he has never stopped chasing down every ball with manic energy. “I’m, like, ‘Come on, just relax,’” quipped his latest victim Aleksandar Vukic on Friday night.

That same evening, Draper revealed that some of his newfound poise can be attributed to his breathing coach. “By having that time off with my hip, I was able to focus on working on a few different things,” he said. “I was working a lot with a breathing coach and just trying to understand that a bit better.

“I had a lot of problems with my sinuses when I was younger,” Draper added, “so I breathe a lot through my mouth. When you are anxious or when you have long points and you have to recover quickly, it’s not efficient to breathe through your mouth.

“I’ve been trying to reverse what I do and breathe through my nose a lot better and a lot more,” continued Draper, who is only the fourth player to win three consecutive five-setters at the Australian Open this century.

“Sometimes you don’t realise how uptight your body is. Especially me, because I’ve always been someone who likes to try hard, and I think sometimes you have to relax. Especially in tennis, because you need to be free to let your muscles do what they need to do. If you’re tense the whole time, you’re not going to last too long.”

The appointment was originally proposed by Draper’s main coach James Trotman, who has guided his career with enormous skill to date. The breathing coach has travelled out to Australia for this event and she has been supporting him throughout.

Draper’s no-stone-unturned approach to his own health and fitness has helped him live up to his seeding of No 15, and thus earn a meeting with world No 3 Alcaraz. He will not be delighted with the scheduling, however, as he was hoping to play in the evening again, which would have given him a few more hours of recovery time.

Instead, the 10-time Australian Open champion Novak Djokovic has been granted the night slot, probably because he wanted to avoid the heat of what is expected to be the warmest day of the tournament so far, with temperatures due to climb to 31 degrees Celsius.

Draper’s afternoon slot – which begins at 3.30pm local time – will make it even harder for him to pull another rabbit out of the hat against Alcaraz. “Hopefully they put me on late against Alcaraz,” Draper had implored on Friday night – or actually Saturday morning, because he did not arrive in the interview room until 2am after his 4½-hour battle with Vukic.

“I need to be aggressive,” he added, when asked about the specific challenges that Alcaraz will set him. “I need to take my chances. Against the top players you get less and less chances to win games and sets and all these sorts of things.

“I need to be brave in the way I play, but I’m expecting him to come out and know that I’ve played three five-setters and that he’s got a battle on his hands. It will be a great contest, I’m sure.”