The former Wimbledon and U.S. Open champion has been undergoing treatment and tests at a Sydney hospital and is waiting on the results to determine when he can resume playing after a month on the sidelines.

"The hip is starting to feel a little better but I'm yet to fully test it out on court," Hewitt said in a statement on Tuesday.

"The specialist did a couple more tests today but the results won't be back for a few days. Once I get those I can make a decision on the French Open and the grass court season."

The hip injury is the latest in a series of setbacks that have plagued Hewitt since he lost the world number one ranking in 2003.

He won the U.S. Open in 2001 and Wimbledon the following season but has not won a grand slam title since and has steadily slipped down the rankings to 19th.