Nadal crashes out in Halle

(CNN) -- Rafael Nadal's Wimbledon preparations suffered a hitch as he fell to a shock straight-sets defeat to Germany's Philipp Kohlschreiber in the quarter-finals of the Gerry Weber Open.

Nadal went down 6-3 6-4 to defending champion Kohlschreiber in the grass court event in Halle, Germany.

Nadal was playing in his first singles tournament since he won the French Open at Roland Garros last week.

The defeat, Nadal's first in 14 matches, continues the world number two's poor record at Halle.

His only previous visit to the tournament, in 2005, ended in a first round defeat to Alexander Waske.

Kohlschreiber, ranked 28 in the world, had never previously beaten Nadal in eight attempts.

Nadal said he planned go back home to Mallorca and recover from a punishing clay court season, ahead of Wimbledon.

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"I can't practise on grass there but it's better not to practise for a few days. It's time to rest with my family, friends, to relax," said the Spanish star.

"I've played almost every match possible since Indian Wells. When I'm ready to come back, I'll go to Wimbledon."

World number three Roger Federer fared better at the German tournament.

He reached the semi-finals with a 6-7 6-4 7-6 win over Canada's Milos Raonic and will face Russia's Mikhail Youzhny for a place in the final.

In the Aegon Championships at London's Queen's Club, Taiwan's Lu Yen-Hsun was forced to retire from his quarter-final against Marin Cilic after playing two matches in the space of a few hours.

The world number 57 earlier clinched a shock 6-3 2-6 7-6 victory over third seed Janko Tipsarevic.

But just a couple of hours later, while was trailing 6-4 2-0 against sixth seed Cilic, he quit with a leg injury.

Bulgarian youngster Grigor Dimitrov joins Cilic in the last four after winning a rain-interrupted clash against South Africa's Kevin Anderson.

He will play David Nalbandian in the last four after the Argentine defeated Belgium's Xavier Malisse 4-6, 7-6 (7/2), 6-4.

In the other quarter-final, 2010 champion Sam Querrey beat Croatia's Ivan Dodig in three sets.