Nick Kyrgios, 21st in the world ranking, was one of the early favourites.
He had a strong last year, went to the final at Wimbledon and is the reigning double champion at the Australian Open.
- Honestly, I'm just exhausted from all this.
It's pretty brutal, of course.
It is one of the most important tournaments in my career.
It has not been easy at all, says the 27-year-old.
Kyrgios' physiotherapist, Will Maher, calls the decision sensible but believes the injury should not be particularly serious.
- It is not a major injury in the way that it would be career-threatening or something like that, he says.
Kyrgio's injury means that he and Thanasi Kokkinakis do not have the opportunity to defend their doubles title from last year.
- It is clear that the timing of this is bad.
Injuries are a part of sport.
I guess I can get inspiration from someone like Thanasi who has had several injuries and bounced back," Kyrgios said.