World No 4 Andy Murray pulled out of next week's Madrid Masters with a back injury, the Briton said on Friday.
"It is with regret that on doctors advice I have to withdraw from the Madrid (event) with an injury," Murray was quoted as saying on the tournament's official website (www.madrid-open.com).
"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 reached the quarter-finals in 2009 and 2010 and the third round last year before falling to Brazil's Thomaz Bellucci.