Curry was omitted from the England squad for Saturday's Six Nations game against Wales and replaced by his brother Ben.
"Tom has a hamstring injury on the opposite leg to the one he did six weeks ago. It's a soft muscle that extends into the tendon and it's four to six weeks," Sanderson said.
"Tom played 80 minutes (for Sale Sharks) on Saturday and (was injured) on Monday — it is something to do with the physical demands of an international camp and he is frustrated."
England, who lost their opener against Scotland and beat Italy in the second game, face Wales at the Principality Stadium in Cardiff on Saturday. They then host France on March 11th and play away to Ireland on March 18th.