Juan Martin del Potro calls foul after time penalty during Novak Djokovic defeat

Juan Martin del Potro is normally the gentlest of giants, but the 6ft 6in Argentine did not hide his anger over a controversial incident here last night (AFP)

Juan Martin del Potro is normally the gentlest of giants, but the 6ft 6in Argentine did not hide his anger over a controversial incident here last night which contributed to his downfall in the semi-finals of the Dubai Duty Free Championships.

Del Potro’s displeasure was sparked as he became the victim of some over-zealous umpiring relating to the time-violation rules during his 6-3, 7-6 defeat by Novak Djokovic, who will meet Tomas Berdych in today’s final after the Czech beat Roger Federer 3-6, 7-6, 6-4.

The time that players are allowed between points – 25 seconds – has not been changed this year, but the penalties for taking too long have been tweaked and are being enforced with renewed vigour. A verbal warning is given for a first violation, and this is followed by a point penalty for all subsequent cases.

Del Potro, 3-1 up in the second set, was preparing to defend break point when Magdi Somat, the umpire, issued him with a time violation. As a result Del Potro, who told Somat it was unfair after a long rally and at such a crucial moment, lost his focus and when the point was played mishit a forehand to drop serve.

The world No 7, who continued to argue with the umpire at the changeover, eventually lost five games in a row. Although Del Potro broke back when Djokovic served for the match at 5-4, he went on to lose the tie-break 7-4.

Del Potro said afterwards that he had only himself to blame for losing concentration and did not dispute that he might have taken too long, but was angry that the umpire had not had a quiet word with him before and had not taken into account the match situation. He said he had told the umpire: “I agree about the warning. It’s OK. No problem. But let me know before and I will agree with you 100 per cent.”

Djokovic sympathised with Del Potro. “I’ve had quite a few warnings myself for time violations,” he said. “I have really nothing against that if the chair umpire previously gives me a heads-up and says, ‘OK, you’re taking a little bit too much time’. But as a chair umpire you need to follow the game. If it’s a long point, you need to have that little amount of tolerance.”

Berdych called earlier this week for on-court clocks to be installed, but Djokovic said: “I don’t think that’s necessary. There is a chair umpire, supervisors, people from the ATP and from the tournament who are watching the match and taking care of the time. You have to respect their decisions, but it all has to be according to rules and fair to the player.”

The tournament was denied the final that organisers and most fans were no doubt hoping for, when Berdych fought back to record his fifth victory over Federer in their last eight meetings.

Federer, who had been 5-2 down in the second set, had three match points in the tie-break but lost it 10-8. Berdych took control of the deciding set after making the only break in the fifth game.