Hosts New Zealand will have to compete in the opening round of the World Cup without two key forwards.
It was confirmed that injured All Black No.8 will miss the opening weeks of the tournament, which gets underway when the Kiwis face Tonga on September 9.
Fellow injured loose forward Adam Thomson looks set to be unavailable for the opening match against their Pacific rivals, Tonga, All Blacks Doctor Deb Robinson said.
Read (high ankle sprain) and Thomson (inside elbow) suffered the injuries in the All Blacks final Tri-Nations Test - a 20-25 loss to Australia in Brisbane last Saturday - and received MRI scans in Christchurch on Monday on their return to New Zealand.
"Kieran has torn the ligament between the tibia and fibula at the front of his left ankle and while it's still early days in his recovery, with aggressive rehabilitation we are aiming to have him available to play near the end of the round robin," Robinson said.
"Adam's MRI scan shows some swelling around the inside of his elbow which should settle quickly," the doctor added.
"He also has some deep bruising to his upper arm and while it's difficult to know how long that will take to settle, we are hoping he will be ready for selection for the All Blacks' second round robin match against Japan."
Read and Thomson will remain with the All Blacks squad as they undergo their rehabilitation.
The All Blacks squad assembles in Auckland on Friday to prepare for the opening match of World Cup against Tonga.
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