A leg injury has forced Lleyton Hewitt to withdraw from next week's Hamburg Masters, disrupting his preparation for the French Open.
Hewitt strained a muscle in his left calf muscle while training last week and despite receiving constant physiotherapy, he has been unable to recover in time.
"We have given Lleyton every opportunity to prove his fitness before embarking on this campaign," Hewitt's coach Roger Rasheed said in a statement.
"Unfortunately he failed a fitness test last night and we've decided to stay home for the next few days, where we believe the best treatment is available.
"With two [Grand] Slams coming up, we're not in a position to take any risks and have adopted a cautious approach."
Hewitt is now planning to resume playing at Portschach in Austria the following week as well as making a rare doubles appearance at this month's French Open to boost his chances of winning a second Wimbledon title.
Although Hewitt has occasionally played doubles in Davis Cup for Australia, he prefers to save his energy for singles, and has not played a Grand Slam doubles since teaming up with Max Mirnyi to win the 2000 US Open title.
But Rasheed told the Daily Telegraph on Friday the former world number one would join forces with fellow Australian Wayne Arthurs at Roland Garros this year to work on his fitness and volleying.
"After his Davis Cup commitments, Lleyton has worked extremely hard to prepare for Hamburg, the French Open and, ultimately, Wimbledon," Rasheed said.
"He's done all the work required for the eight weeks ahead of him with a view to peaking at Wimbledon."
Hewitt won the Wimbledon singles crown in 2002 and the US Open the previous year but has not won a Grand Slam title since. He reached the US Open final in 2004 and the Australian Open final in 2005.