SOFIA (REUTERS) - Bulgarian world No. 4 Grigor Dimitrov said he would not defend his title at next week's Sofia Open as he has failed to recover from a shoulder injury.

"I and my team had to take one of the most difficult decisions - to skip this year's edition of the tournament in Sofia," Dimitrov said in a statement.

"Earlier today, I had my last medical consultation. Unfortunately, I will not be at 100 per cent ready for next week. If I play, it would lead to additional risks and complications."

Local favourite Dimitrov will be replaced by Swiss Stan Wawrinka, who is trying to resurrect his career after suffering a knee injury.

"On back of disappointing news of Dimitrov injury, great that three-time Grand Slam champion Stan Wawrinka will play Sofia Open," the tournament director Paul McNamee said on Twitter.

South Korea's Chung Hyeon will also miss the tournament after failing to recover from the foot injury that forced him to retire from his Australian Open semi-final against eventual champion Roger Federer.