Former world No. 1 Andy Murray has suffered another injury setback and has pulled out of this week's ATP Tour event in Germany due to a lingering pelvic problem, raising doubts over his participation for the remainder of the year. 

The three-time Grand Slam champion played the first of back-to-back events in Cologne, where he was knocked out in the first round by Fernando Verdasco last week. 

He said he was suffering from tendonitis in his left psoas, the muscle which connects the lower back to the top of the leg. 

"It's been kind of on and off since the U.S. Open," Murray said in a video message on Facebook posted on Sunday. "I've been trying to deal with it in training, and in the matches, and unfortunately after my match here this week it's flared up again."

"I've been practicing the last few days and trying to manage it, but after playing some points today, I decided that it was not going to be good enough to play." 

Murray, whose ranking has slipped to 116th in the world, did not clarify if he would seek a wildcard in the ATP Masters event in Paris in two weeks and the subsequent event in Bulgaria. 

"I will see you on the court soon," Murray signed off, without specifying how long he will be out for. 

The Briton returned from a second hip surgery in January 2019 to win the Antwerp title seven months later - his first since 2017 - raising hopes of a return to the top echelons of men's tennis. 

But the 33-year-old again suffered complications with his hip following the Davis Cup in November and only returned to the circuit after the lengthy COVID-19 pandemic break. 

He also fell in the opening round of the French Open after suffering a second-round defeat in the U.S. Open. 

(With input from Reuters)