Park Ji-Sung's return has been put on hold after the South Korean midfielder suffered an injury in training.The squad had been playing without him for the past six weeks while he was at the Asian Cup in Qatar, and he now faces another month on the sidelines.
Park injured a hamstring injury on Friday ahead of the Manchester derby, and will now miss United's European Champions League last-16 clash with Marseille in France on February 23.
"It was very unfortunate because it was his last kick of the ball in training," said Sir Alex Ferguson on Tuesday.
The winger has not played for the English Premier League leaders since the 2-0 win over Sunderland on December 26.
Park was part of the South Korean squad which reached the semifinals of January's Asian Cup before losing to eventual champions Japan.
Park will also miss Saturday's FA Cup fifth-round match with non-league minnows Crawley Town as well as Premier League trips to Wigan, Chelsea and Liverpool, but may be back in time for the second leg against the French champions on March 15.
In better news for United, Ecuador winger Antonio Valencia is back in training after breaking his ankle in a Champions League match against Scottish side Rangers in September.
"Valencia started training with the reserves on Saturday," Ferguson said. "So he's on his way back and that will be a real boost to have him available for the run-in."
