The former England captain limped off in the second half at The Hawthorns and manager Sir Alex Ferguson revealed after the game Ferdinand will miss six weeks, meaning he will be out until the start of October.
It means the 32-year-old would miss the games against Arsenal and Chelsea and England's two Euro 2012 qualifiers against Bulgaria and Wales.
Fellow central defender Nemanja Vidic also succumbed to injury on Sunday, struggling with a calf problem with the opening minutes before eventually coming off just after half-time.
It all adds up to serious defensive concerns for Ferguson who has also lost Rafael for 10 weeks after he dislocated a shoulder in training.
Ferguson told Sky Sports 1: "We've had a rough time with injuries.
"Young Rafa has done his shoulder in training in Friday and will be out for 10 weeks, he's probably going to have an operation.
"Rio will be out for six weeks. Vida will have checks tomorrow, we don't know if it's just a nerve or something, but he could be out for a couple of weeks."