Tomas Berdych has said that securing the first set in his Madrid Open quarter-final against Andy Murray was vital in his defeating the British number one.

The Czech recovered from a slow start to take the opener to a tie-break, which he edged, before taking the second set 6-4.

"Even though I didn't start well I was able to turn the first set on my side, which was very important," Berdych told reporters.

"You know, with [Murray] it's never easy. Even though we played just two sets they were really long. You really have to fight a lot for a small chance."

Murray admitted to feeling some fatigue following his drawn-out clash with Gilles Simon the night before, but refused criticise the tournament schedule.

"I did play a very long match yesterday and finished extremely late so I was a bit stiffer probably than usual at the beginning but once I warmed up it felt better," said the Scot.

"The Spaniards like starting late so you've just got to deal with it."

Berdych will face either Stanislas Wawrinka or Jo-Wilfried Tsonga in the semi-finals.