Dubai: World No 2 Rafael Nadal has questioned the efficiency of the new Hawk Eye line calling technology.

Thursday's first set between Nadal and Youzhny ended in a controversy with the tie-break score at 6-5 in favour of the Russian. Nadal thought a ball from the Russian had landed wide.

So the Hawk Eye was pressed into service and it showed the ball had skimmed the line.

But Nadal, chair umpire Roland Herfel of Germany and even Youzhny believed that the ball had landed wide after watching the Hawk Eye. But officials are bound to accept the Hawk Eye ruling.

"The mark of the ball was still on court and it was outside. But in the challenge it was in, so that's unbelievable. The Hawk Eye system is not perfect," fumed Nadal.

"I told the chair umpire: 'Look, the ball is out' and he said: 'I know'.

"The truth is that the ball was out. Let them put the Hawk Eye on clay and you will see," Nadal shrugged.

Pushing up

"I am not against the Hawk Eye. I know it is good for the sport and better for the involvement of the spectators. It helps push up the level of the show on court."

Even Youzhny agreed the ball appeared to have gone out. "I saw the mark, but I just challenged because it was a very important point," the Russian said.

"I was a bit surprised when the Hawk Eye showed the ball to be good. But anyway, you can have the same mistakes from the linesmen or the chair umpire," Youzhny offered.

Top seed Roger Federer too had a bad taste in the mouth - thanks to the Hawk Eye in his match against Novak Djokovic, who challenged on match point in the second set. The Serbian went on to take the set on tie-break, only to see Federer come back and win the third by breaking in the eighth game and then served out for set and match 6-3.

Besides these rare instances, the Hawk Eye has been an enjoyable experience for tennis lovers at the Dubai Tennis Stadium.

The Hawk Eye line-calling system is one of the innovations implemented at this year's Dubai Tennis Championships.