Draper has not played a competitive singles match since his surprise Wimbledon second-round exit in early July.
He pulled out of the Canadian Open and Cincinnati Open – both key ATP tournaments leading up to the US Open – in order to fully recover from the arm issue.
After starting to feel a problem during the clay-court swing, he said it got “progressively worse” over the grass-court season which culminates at the All England Club.
However, he was loath to blame the injury for his Wimbledon defeat by veteran opponent Marin Cilic.
“I felt like my arm was shutting down a little bit when I was hitting forehands and on the serve,” said Draper.
“It got progressively a bit worse. Then on the grass it got quite painful. I didn’t know what I was dealing with.
“After the grass, I got it checked out. It is one of those where if you keep playing with it, it could become very, very serious.
“Saying that, it was not so bad because I could do a lot of other things as well physically. It wasn’t like I had to stop completely.”
Draper returned to the match court when he played alongside American Jessica Pegula in the new-look mixed doubles at Flushing Meadows.
While it did not look like Draper went full throttle on his serve as the pair reached the semi-finals, he said it was “perfect” preparation.
“In tennis, having a month and a half out is quite a long time,” he said.
“I definitely feel a lot sharper having played that as opposed to maybe having a training week.”
