JERZY JANOWICZ astonished a gathering of reporters when he thundered away from the Aorangi Park practice courts yesterday muttering little more than monosyllables.

But those who know him best were anything but surprised by such behaviour.

The 22-year-old from Lodz with a reputation for arrogance is an explosive character at the best of times – as witnessed by the full-blooded war cry he emits upon victory, or the full-blown meltdown he experienced during this year's Australian Open over a disputed line call against India's Somdev Devvarman. Janowicz likes to go for a nap in mid-afternoon and said he would not speak to press yesterday. Therefore, he did not speak to press.

Fortunately his Finnish coach, Kim Tiilikainen, who reached the cusp of the world's top 200 as a player, was not quite so reticent about his charge, who today takes on Andy Murray for a place in Sunday's Wimbledon men's singles final.

In Tiilikainen's eyes, Janowicz's demeanour projects confidence rather than arrogance. And, having won his last meeting with Murray – a last-16 match during the Pole's breakthrough run at the Paris Masters in October – he feels such confidence is well founded.

"With the way he walks it might look like arrogance, but I would say it is just confidence, and he is not just trying to pretend he is confident: he truly believes he can beat anyone, and that he can win the tournament. He believes he can beat Andy, but of course he has to play well to do so," said Tiilikainen.

The Finn – also Finland's Davis Cup captain – has learned to live with the 22-year-old's foibles in order to burnish his abilities on the court. "Jerzy is an emotional person who reacts the same way to things in his normal life, and it is very nice to see someone who is not trying to pretend he is anything other than what he really is," Tiilikainen said. "Tennis needs characters like this. We have had so many years together and we know each other so well that I know when to be quiet and when I can talk to him. He is not like a robot where you just have to turn him on in the morning."

Janowicz himself admits he is "an explosive character and a pure fighter" who doesn't "need to play aesthetically well all the time" as long as he can grind out victories. The really bad news for the Scot is that his game is as explosive and volatile as he is. That 6ft 8in frame and high ball toss allows him to hit parts of the court on service which others simply cannot reach, his 140mph top speed is the best in the tournament and he has served 94 aces so far, 34 more than the Scot.

While he has also served 26 double faults, more than any other remaining man, the Pole has been broken just four times to the Scot's seven. In addition, there is that dangerous flat forehand, the imagination to mix things up with a drop shot or two, and twinkle-toed movement which belies a man of his height. In his run to the Paris Masters final – during which he stayed well away from the other players, barely slept between matches and fuelled himself on a diet of croissants – he beat five top-20 players before eventually losing to David Ferrer. He left his opponents regularly complaining about their inability to get into a rhythm. For Wimbledon he is staying at Chelsea Village, but is no football fan. "His game was unpredictable, powerful, joyful and confident so there was no sense to take the risk and make him think of the opponents or tactics too much when it was all about him," recalled Tiilikainen. "He just played such a unique and strong game that the other players didn't know what to do. You could see in many matches how his opponents got frustrated. His game was unpredictable and powerful; he was serving great and no-one liked it."

For all his formidable physical assets – even if his serving arm is bandaged with physio tape – the Pole has done well to make such giant strides. A former US Open junior finalist, on his return to Flushing Meadows two years ago expatriate countrymen in New York had to chip in to buy him shoes, while 18 months ago he could not even afford flights to compete in Australian Open qualifying.

Wimbledon will be his first grand slam semi-final, although he has met Murray on these shores before, a straight-sets loss in the Davis Cup at Liverpool's Echo Arena in 2009. "He will love it," said Tiilikainen. "He does not like to play on an outside court. He is born to be a star."

Kyle Edmund, the 18-year-old Briton who was Janowicz's first-round opponent, as well as being the Scot's sometime hitting partner, said Murray would have to be at his best. "He's a very big threat," said the Yorkshireman. "I just like his freedom. It seems like he doesn't worry too much about what the score is. You get his serve back, which is obviously a challenge in itself, and then wherever it goes, forehand or backhand, you know it is going to come back with interest. It's a constant pressure."

Janowicz feels this is his moment. "I have had some troubles during my career," he said. "This is what I have been waiting for, dreaming about. Sometimes if you dream about something really hard, it can actually happen."

Janowicz's dream really would be Murray's nightmare.