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Rapoport added that the surgery is scheduled for Monday and will repair a torn labrum.
Per Rapoport, Armstead suffered the injury during mandatory minicamp Wednesday before undergoing testing Thursday.
Armstead was a third-round pick out of Arkansas-Pine Bluff in 2013, and he has been New Orleans’ starting left tackle for the past three seasons.
While he is often dominant when healthy, Armstead has struggled to stay off the injured list.
The 26-year-old missed five games combined in 2014 and 2015, and he was forced to sit out nine contests last season due to multiple lower-body injuries.
Armstead’s current timetable to return could see him get back on the field anywhere from October to December.
Regardless of when he comes back, Armstead will likely start the season on the physically unable to perform list or on injured reserve with the possibility to return.
With Armstead on the shelf, veteran Khalif Barnes and rookie first-round pick Ryan Ramczyk figure to battle it out for the starting job.