Novak Djokovic's disdain for the blue clay was all too apparent as he fell to a straight-sets defeat to Janko Tipsarevic at the quarter-final stage of the Madrid Open.

379382 - Tipsarevic topples listless Djokovic in Madrid

Djokovic was unlucky to lose the first set, consistently producing the higher quality but failing to convert the pressure points - however, in the second Tipsarevic sparkled while Djokovic, who has complained about the blue clay this week, looked laboured and uncomfortable.

Tipsarevic won 7-6(1) 6-3 to send the defending champion tumbling out, a result which blows the tournament wide open.

"I want to forget this week as soon as possible and move on to the real clay courts," Djokovic said. "It took me at least a week to try to get used to this surface and somehow find a way to win matches and play a decent level of tennis. There is no discussion in my eyes, it's very simple. No blue clay for me."

The difference between the players' service games was stark early in the opening set: Djokovic was cruising untroubled through his, whilst Tipsarevic was being forced to lean on all his defensive resilience, clinging onto each game for dear life. Yet the lesser-ranked man was just about fighting off the tide, and he battled all the way to a tie-break.

As if realising that his herculean resistance could not be wasted, Tipsarevic romped away with the tie-break to claim the first set - and put himself on a track for only a second career victory over his countryman. Djokovic's unease on the surface was particularly apparent during the final exchanges, as he frequently pottered around on unsteady footing.

The start of the second frame was similar to the first until - and there had been no real hint this was about to happen - Tipsarevic, who had no break points in the first set, won a game against serve to move 4-2 up. Djokovic looked resigned to his fate initially before conjuring a late rally which he was, ultimately, unable to sustain.

Tipsarevic will play world No. 3 Roger Federer in the semi-finals.

The other semi-final will be between No. 6 seed Tomas Berdych and Juan Martin del Potro, the tenth seed. Berdych got the better of Fernando Verdasco, Rafael Nadal's conqueror, 6-1 6-2 in just 67 minutes, continuing his record of not losing a game on serve at the tournament.

Meanwhile, Del Potro took 84 minutes to record a 6-3 6-4 victory over Alexander Dolgopolov, which continues his unbeaten record on clay this year and marks him out as one of the men to beat at the French Open later this month.