LONDON: Frustrated fans were left wondering quite what was the point of Wimbledon's 80 million-pound ($101 million) Centre Court roof on Monday when Novak Djokovic's match was delayed for over an hour as ball boys took to using leaf blowers to dry the grass.

Defending champion Djokovic had just taken the first set 6-3 against Argentina's Pedro Cachin when light rain forced the players off and led to the roof being slid into place - a process that takes 10 minutes.

Fans and TV viewers expecting a quick resumption, however, were to be disappointed as, accompanied by tournament referee Gerry Armstrong, Djokovic patrolled the famous square of grass he has ruled for five years, dabbing a toe and a towel at areas he considered dangerously slippery.

Leaf blowers were eventually used to try to dry the turf before, somewhat bizarrely, the roof, completed in a blaze of publicity in 2009, was reopened and the match resumed in the open air after a 70-minute delay.

Strangely play resumed much sooner on Court One under the roof, leaving Djokovic a little mystified as he spoke to media after his routine 6-3 6-3 7-6(4) victory.

"It normally takes 10 to 20 minutes when the roof is closed for the air conditioning to do its job and grass to dry and to be ready for play," Djokovic said.

"We saw that players came back after maybe 15 minutes to Court One, and they resumed play. But we didn't and we couldn't really. Too many places on the court were too slippery and really moist. Touch the grass and your palm is completely wet.

"It was very strange that for more than an hour the situation was not changing at all for the better.

"We had fun with it. We received the good news that they will open the roof, then wind obviously did its job."