LONDON • Novak Djokovic yesterday claimed a straight-sets victory over Adrian Mannarino, beating him 6-2, 7-6 (7-5), 6-4 in the round of 16, but had concerns about the state of the Centre Court surface at Wimbledon, claiming there was a hole on the baseline.

The Serbian world No. 4 made his worries about the court known to the umpire Carlos Bernardes - and revealed the man in the chair was unimpressed by what he saw.

"I mentioned that there is a hole in the middle of the court, the middle of the service line, and he just asked me to show him," said Djokovic after the match. "I did and he was not very pleased to see that.

"The courts honestly are not that great this year and many players feel the same, but it is what it is. Grass is probably the most complex surface to maintain. It's not easy."

The fourth seed struggled against a player ranked 51st in the world and midway through the third set he sought treatment for what looked to be a shoulder problem.

Asked about his injury, Djokovic said: "It's been something I've been dragging back and forth for a while now but I'm still managing to play, which is the most important thing."

Djokovic broke Mannarino twice in an entertaining first set lasting 37 minutes thanks to the left-handed Frenchman's durability in the rally.

The question was whether Mannarino, who had never reached the quarter-finals of a Grand Slam, could maintain his spikiness into a second set.

Djokovic again broke him easily at the first time of asking. But once again, the Frenchman seemed liberated by the loss and began to dominate the rallies.

A tie-break beckoned and both players wanted it, with each of the first five points resulting in a mini-break. But gradually, Djokovic reasserted himself and won 7-5.

The match was taking longer than Djokovic had intended and his frustration boiled over at the beginning of the third set when he hit a ball into the ground after dropping a point on his serve.

The crowd responded with a pantomime "ooooh" and it seemed to sort Djokovic out. He played more steadily to wear down Mannarino and move into the last eight.

"I haven't dropped a set yet on grass this season either here or in Eastbourne. I am motivated to go as far as I can," said Djokovic.

The Serb will face the Czech Republic's Tomas Berdych today for a semi-final spot, boasting a 25-2 career record over the 2010 Wimbledon runner-up.

THE GUARDIAN, AGENCE FRANCE-PRESSE