Taiwan’s Lu Yen-Hsun has been forced to quit his Queen’s Club quarter-final against Marin Cilic as the strain of playing two matches in the space of a few hours took its toll.

Lu had clinched a shock 6-3 2-6 7-6 (7-5) victory over third seed Janko Tipsarevic earlier on Friday to reach the last eight at the pre-Wimbledon warm-up event for the first time.

But the Tipsarevic match had been carried over from the previous day due to rain, meaning the world No.57 had to return to action only a couple of hours later to face Cilic and his body was unable to cope.

The 28-year-old was already trailing 6-4 2-0 against sixth seed Cilic when he decided to withdraw from the match with a leg injury.

Lu had landed an early blow in his first ATP quarter-final this year when he broke Cilic in the second game of the opening set.

But that only sparked Cilic into life and the Croat hit straight back, breaking in the next game and again in the fifth to move 3-2 ahead.

That was enough of an advantage for the big-serving Cilic to close out the first set and he was back on the attack with another break at the start of the second.

Lu was showing signs of discomfort as he moved now and he called for treatment at 2-0 down.

The trainer spent several minutes working on his groin area, but Lu still seemed unhappy and was soon on his feet to tell Cilic that he would have to withdraw.

With the top five seeds here already eliminated, Cilic – who will face 2010 Queen’s champion Sam Querrey or Croatia’s Ivan Dodig in the semi-finals – must fancy his chances of winning the tournament.

Earlier, Bulgarian youngster Grigor Dimitrov reached the last four as he won a rain-interrupted clash against South Africa’s Kevin Anderson.

Dimitrov, a former junior champion at Wimbledon and the US Open, is regarded as one of the rising stars of the ATP Tour and he underlined his credentials by coming from a set down to beat ninth seed Anderson 4-6 6-4 6-3.

The 21-year-old, who is making his Queen’s debut, is so lavishly talented he has occasionally drawn comparisons with Roger Federer, but he is only just beginning to deliver on that promise.

This was his first ATP quarter-final of the season and he seized the moment with a dynamic performance in between the showers that forced play to be halted twice.

Dimitrov will play either 2002 Wimbledon finalist David Nalbandian or Belgium’s Xavier Malisse in the last four.