"Even though I have been working hard with my team and my medical staff, we have now had to make the difficult decision that I will not be able to compete at the US Open this year," the Italian said in a statement.
"We have been back on court in Monte Carlo over the last couple of days and have realised that I still need more time to recover from my right knee issue. The five-time Grand Slam winner has not played since winning Wimbledon on July 12, pulling out of US Open warm-up hard court tournaments in Cincinnati and Montreal.
