Americans call him "the Djoker". While some of his rivals have not always appreciated Novak Djokovic's brilliant impersonations of his fellow players – it is said that Roger Federer does not see the funny side – the US Open crowd love the 23-year-old Serb.
His outgoing personality appeals to the New York public and at most socials he is the life and soul of the party.
For a while there seemed to be a danger that the world No 3 would be celebrated more for his party pieces than for his tennis. Although he reached his first Grand Slam final at the 2007 US Open and won his first major title four months later here, he appeared to have reached a plateau. He still won his fair share of lesser tournaments, but when it came to the Grand Slam events he kept falling short.
That changed at last year's US Open, where Djokovic won a titanic battle against Roger Federer before losing to Rafael Nadal in the final. He maintained that form through to the end of the year, leading his beloved Serbia to a historic victory in the Davis Cup. Past problems with his breathing and stamina appear to have been largely overcome.
How does the Djokovic of 2011 think he compares with the 2008 vintage? "I'm three years older and I'm a more experienced player on the court and physically stronger," he said. "I was a 20-year-old kid hitting as hard as he could with closed eyes and everything was going in back then. It was great.
"Then, over the years, I faced some situations that I never faced before, like the pressure of defending a Grand Slam title. You grow up. You get this knowledge and the necessary experience.
"I had my ups and downs throughout these two or three years, but right now I feel like I'm much stronger and more consistent and I know that I'm more stable, mentally and physically."
Djokovic has won four of his 18 titles on clay, but his other successes have all been on hard courts, which suit his style as a hard-hitting baseliner. While clay is a better surface for players who hit the ball with more topspin, Djokovic's flatter strokes, hit lower over the net, are more effective on courts where the ball accelerates quickly off the surface.
"I like this surface," Djokovic said of the courts here at Melbourne Park. "The conditions are very suitable to my game. It's a bit slower and gives me enough time to have a couple of options in what I want to do with the ball. I can spin it out, flatten it out. I need a little bit more time for my game, and the slower surfaces are more suited to my style. This is a great court. I like playing on it."
Djokovic comes from a family of skiers, but from an early age his talent for tennis was clear. He left his Belgrade home at the age of 12 to train at Niki Pilic's academy in Munich. He now lives in Monte Carlo, but remains a fiercely patriotic Serb.
Tale of the tape: Djokovic / Murray
Djokovic: Belgrade, Serbia, 22 May 1987
Murray: Dunblane, Scotland, 15 May 1987
Djokovic: Monte Carlo
Djokovic: 6ft 2in
Murray: 6ft 3in
Djokovic: 12st 8lb
Murray: 13st 3lb
Djokovic: Marian Vajda
Murray: Alex Corretja
Djokovic: $20,262,956 (£12.8m)
Murray: $13,967,298 (£8.8m)
Grand Slam Best
Djokovic: Won Australian Open 2008
Murray: Runner-up US Open 2008, Australian Open 2010
Djokovic leads 4-3
2006 Madrid (hard) Djokovic won 1-6, 7-5, 6-3
2007 Indian Wells (hard) Djokovic won 6-2, 6-3
2007 Miami (hard) Djokovic won 6-1, 6-0
2008 Monte Carlo (clay) Djokovic won 6-0, 6-4
2008 Toronto (hard) Murray won 6-3, 7-6
2008 Cincinnati (hard) Murray won 7-6, 7-6
2009 Miami (hard) Murray won 6-2, 7-5