Andy Murray has pulled out of next week's Masters 1000 tournament in Madrid with a back injury.
The world number four will hope to return to action at another Masters event in Rome the following week as he builds up to the French Open, which begins on May 27.
Murray said in a statement, posted on the tournament's official website: "It is with regret that on doctor's advice I have to withdraw from the Mutua Madrid Open with injury.
"I always love coming to Madrid so it is a big disappointment. I look forward to returning next year and wish everyone a great week of tennis."
Murray has shown decent form on the clay this season, reaching the quarter-finals in Monte Carlo and Barcelona, although on both occasions he was beaten by lower-ranked players - Tomas Berdych and Milos Raonic.
The 25-year-old Scot won in Madrid in 2008 when it was an indoor hardcourt tournament but has not made it past the last eight since its switch to clay three years ago.
This year's tournament will feature defending champion Novak Djokovic, home hope Rafael Nadal and Roger Federer, who will be playing his first claycourt event of the season.
Djokovic will face a qualifier in his opening match and is on course for a meeting with Federer in the last four. The Swiss faces a tricky opener against either rising star Milos Raonic or former French Open semi-finalist David Nalbandian.
Nadal is on the other side of the draw and will open against Ivo Karlovic or Nikolay Davydenko.
The Spaniard is now due to meet Jo-Wilfried Tsonga in the semis with the Frenchman having claimed what would have been Murray's number four seeding.
The men's action gets under way on Sunday.
The women's draw was also made on Friday with world number one Victoria Azarenka drawn in the same quarter as reigning French Open champion Li Na. Azarenka starts against a former Roland Garros winner, Svetlana Kuznetsova and is seeded to meet Agnieszka Radwanska - a player she has beaten five times already this season - in the last four.
On the other side of the draw, Maria Sharapova is seeded to meet defending champion Petra Kvitova in the semis.
However, this half looks much tougher with Kvitova on course to meet Sam Stosur in the last eight. Sharapova, a winner in Stuttgart last weekend, is likely to play the winner of the scheduled last-16 blockbuster between Caroline Wozniacki and Serena Williams in her quarter-final.
The women's main draw action begins on Saturday when the venue's new and controversial blue clay will be tested in a competitive match for the first time.
Early reports suggest it is playing lower than its red counterpart.