From hothead to warrior - Draper's journey to US Open semis

Like the majority of teenagers, Jack Draper could sometimes sulk on the tennis court.

There would be the obliteration of racquets. There would be furious self-castigations. There were occasions where an apology to the umpire might be needed.

All that was part of the growing up process. And it has been a key part of the 22-year-old Briton's journey to becoming a US Open semi-finalist.

"His temper boiled over at times," remembered Justin Sherring, the coach who developed Draper between the ages of five and 15.

"Did I have to call his racquet manufacturer a few times and say 'oops, I think Jack's racquets have snapped on the stringing machines that we've got here in India'? Yes.

"Did we have cross words a few times? Yes we did.

"But that's how it goes. Looking back, I'm so glad he did that.

"When you have this burning desire and feel greatness rumbling in your soul, you get frustrated."

Minor disagreements happened. They always do between teenagers and adults assuming guiding roles.

The tales are told now by both Draper and Sherring with a laugh. There is an understanding these escapades were instrumental in shaping the British number one's career.

Once there was a post-argument duel with water guns - Draper's way of diffusing the tension - with his coach in a American hotel corridor.

It happened at the prestigious Orange Bowl youth tournament, where Sherring realised Draper was "quite nervous" during a match.

With things not panning out as they hoped, the youngster flipped the middle finger at his coach.

That was permissible considering the pair's strong bond. But Draper's "monkeying about" after the game resulted in him having to walk back to the hotel as Sherring "needed some space".

"Half an hour later, there is a knock on the door and it was Jack wanting to clear it up," Sherring told BBC Sport.

"I opened the door and he's got a water gun and starts zapping me with water.

"There was another one of the floor - he left one for me, which was quite considerate - so I picked it up and chased him.

"I thought 'is this how you normally make up after an argument? Is this what I'm in for?"

One of the most interesting things to observe during Draper's run in New York has been his cool demeanour.

Whether he has rolled over another opponent in his breakout run at a Grand Slam tournament, or is posing for Instagram content in Central Park, he has stayed calm.

Even as recently as this year, it has not always been the case. Nerves have still lingered for Draper on the big occasions.

At the Australian Open he was sick at the side of the court because of the tension he was feeling on the way to winning his first-round match.

On the French Open clay, a dejected Draper was particularly demonstrative and - in Sherring's words - "throwing his toys" during a chastening first-round defeat by Dutchman Jesper de Jong.

So what's changed and how has it changed so quickly? Draper's current coach James Trotman explained after the quarter-final victory against Australia's Alex de Minaur.

"It does take the experience of being exposed to it, understanding how the momentum is going to swing, the concentration flows in the matches," he said.

"I just think he's maturing all the time. He's secure with his game, he understands that he can't go out and burn all of his energy and all of his emotions early on.

"It's just a sign that he's becoming more comfortable on this stage and playing with the best players in the world."

Draper, born and raised in Surrey, comes from strong tennis stock.

His mother Nicky - who the player credits as one of his biggest influences - is a coach and former junior champion, while father Roger was the chief executive of the Lawn Tennis Association.

Older brother Ben was a former college player in the United States and now looks after his sibling's interests as his agent.

Thumping a tennis ball against the garage door at the age of one, which his mother says happened because he was copying his brother, was the first sign that Draper possessed the talent.

A few years later, she took the boys down to Weybridge Tennis Academy where Sherring - a long-time friend of the Drapers - was the lead coach.

"I thought we were going to focus on Ben, so I had a hit and he was pretty good," Sherring said.

"Nicky asked if I could have a hit with Jack because they were looking for a coach for him. I said 'yes, but he’s quite little and quite young'.

"A hundred shots later I went 'wow'."

Draper stayed under Sherring's tutelage for the next decade and the pair travelled around the world to hone the player's craft against other prodigiously talented youngsters.

Largely they trotted around Europe, as well as trips to the Orange Bowl and ITF events in India.

Ensuring Draper maintained his education was a key priority for his mother, however, who asked Sherring to teach him 10 words each day.

"Depending what mood I was in, or what mood he was in, I would think of a word that he might have been that day, like obstinate," he laughed.

"He'd ask what it meant and I'd say 'well, you've been it all day, look it up and come back to me'."

The teenager, however, only wanted to study tennis.

Travelling back from losing to a Russian youngster at an event in Sweden, Draper questioned why he was still going to school when his opponent was already training professionally.

That was the beginning of his transition from leaving Reed's - an independent boys' school in Surrey which also counts Tim Henman and Hollywood actor Tom Hardy as notable alumni - to home education.

"He started wondering what he was going to school for, why he is hanging out with other kids, why he is doing what others are doing, it was frustrating for him," said Sherring.

"Then he lost to some muppet - in his words - after flying halfway across the world.

"But that's how it goes. You wouldn't see the warrior you see now if it had been all sunshine and roses, or strawberries and cream."