ABU DHABI // Inside the short tunnel, a team of six ball boys and girls waited patiently to enter the sold-out stadium at Zayed Sports City.
As they entered in their blue uniforms, waving and smiling, the crowd replied with camera flashes and loud cheers. It was a clear signal to yesterday's 5,000-strong crowd that the three-day Mubadala World Tennis Championship was about to begin.
For some of the 30 youths participating, it was their first time on the court with many of the world's best players. Andy Murray, the Olympic gold medallist, US Open champion and world No 3, opened the event, but suffered a shock first-round rain-affected 3-6, 4-6 defeat against world No 9 Janko Tipsarevic.
Ben Scholz, a 16-year-old from the US, admitted to having butterflies in his stomach before going out.
"For the past few weeks we have been practising and fixing our mistakes," he said. "For a such a big tournament like this, it is nerve-wracking."
Over the past few nights Ben had played out events in his head. "I play tennis on the Wii and try to imagine if the ball goes out, I wonder what I have to do," he said.
Roberto Rubio, who is charge of the ball boys and girls, said getting chosen as a ball boy or girl was not an easy task. Trials were held at the PSS Tennis Academy in Zayed Sports City over four weeks and hopefuls were whittled down from 45 to 30. Not only were organisers looking for good ball coordination, they needed boys and girls to be confident and possess a certain sparkle for the centre court.
"There's more to it than picking up balls," Mr Rubio said. "There are a series of hand signals from the players for when they want water, a towel or a ball."
There are different rules to be aware of: only six balls are allowed on the court at one time and during a tie-breaker, the youngsters must get the balls around as quickly as possible without disrupting the flow of the game. Players can also have different signals for the same thing, according to Jeff Vanden Auweele, a ball boy for the second consecutive year.
The 13-year-old Belgian said some players might put their palm out for a ball and backwards for a towel. Others will pretend to wipe their face for a towel. Others will point their racket at the ball boy for a ball.
Liana Rais, 16, said she was nervous, despite this being her fourth time as a ball girl. But "you are really focused once it starts", the British-Indonesian said.
The five teams of six ball boys and girls are rotated after 30 minutes on court. There is one in each corner and one at each end of the net. Balls are collected at the net and elsewhere and then rolled back to the corners when there is a break in the play.
"It can be really tiring because you are out in the heat and when they are practising their serves at the start, you have to dodge the balls," she said.
Liana was not so lucky two years ago when she got hit on the shoulder by a ball moving at more than 100kph. Last year she was in charge of holding the sun umbrella for the players.
"I couldn't open the umbrella, and it was right in front of the camera," she said. "It was so embarrassing." She came back, however, "because it is fun".
Novak Djokovic, the No 1 player in the world, was their favourite.
Jeff, who got lucky last year, said he was hoping for another photo opportunity.
"I was serving Rafa Nadal [a bottle of water] and my mother took a photo of me smiling at him and him smiling back at me," he said.
It is now his Facebook profile photo and this year he hopes to replace it with Djokovic.