Djokovic struggles into Dubai quarters

Top seed Roger Federer had no such difficulties against Spaniard Marcel Granollers, winning 6-3 6-4 with a flurry of spectacular winners to reach the quarter-finals.

Second seed Djokovic won 6-3 2-6 6-4 but the outcome hung in the balance until the final few minutes as Lopez, who reached the final in 2004 and 2008, tormented Djokovic with a varied and aggressive game.

Serb Djokovic took the opening set with just one break of serve, leading 3-1 when Lopez double-faulted, but he was quickly in trouble in the second.

Lopez broke to love in the second game and Djokovic was unable to respond as his opponent made frequent approaches to the net and showed greater persistence and accuracy.

A further break for 6-2 closed out the set but Djokovic began strongly in the third, showing more aggression as he forced a forehand error to break for 1-0.

Lopez levelled at 3-3 but Djokovic regained the advantage on his third break point in the next game and that proved decisive.

“It’s been an exciting match, to be honest, even though I was struggling,” Djokovic told reporters. “I don’t think I’ve played bad, actually. He played really well in the second set. I did make some unforced errors, but the match turned around and he felt the momentum and he was playing better than I did most of that second set.

“To be honest, I was a little bit surprised with the way he was returning. He was getting a lot of balls back and he was making me play an extra shot.”

Eighth-seeded Latvian Ernests Gulbis lost 6-3 5-7 6-1 to Sergiy Stakhovsky of Ukraine and third seed Czech Tomas Berdych defeated Russia’s Nikolay Davydenko 6-3 7-6.

Also through to the last eight are Richard Gasquet, a 6-2 7-5 winner over Sergei Bubka, Florian Mayer, who dismissed Andrey Golubev 6-3 6-4, Gilles Simon, who defeated Lukas Rosol 6-2 6-3, and Philipp Petzschner, who beat Philipp Kohlschreiber 6-0 4-6 6-2.