The Bulgarian experienced a shoulder injury that affected him at the Australian Open, and said that he had consulted with doctors before withdrawing.
"I and my team had to take one of the most difficult decisions to skip this year's edition of the tournament in Sofia," said Dimitrov in a statement. "I will not be at 100 percent ready for next week."
However, the tournament director Paul McNamee said the event had found another top name in Wawrinka. The three-time Grand Slam champion appears to be looking for more tournament play as he returns from knee surgery.