Bad news for the Saints. Left tackle Terron Armstead has suffered a torn labrum and will require surgery, Ian Rapoport of NFL.com tweets. The timetable to return is 4-6 months. 
The Saints can be expected to explore out-of-house options now that their starting left tackle will be out for at least the early portion of the season. Ryan Clady is perhaps the best free agent tackle left in free agency. Will Beatty and the versatile Austin Pasztor are also available.
Alternatively, the Saints could promote from within and move first round pick Ryan Ramczyk from the right side to the left. Zach Strief, who was supposed to be the main backup to Armstead and Ramczyk, could slide into the starting role at right tackle. However, in a year where the Saints are hoping to get back into the championship picture with Drew Brees and Adrian Peterson, it stands to reason that they will want some better protection on the O-Line.
Armstead, 27 in August, missed nine games due to injury in 2016. However, he still graded out as Pro Football Focus’ No. 21 tackle on the year. In 2015, Armstead played in 13 of 16 possible regular season games and earned one of the highest scores of any tackle in the NFL.
I see Ramczyk replacing him but the Saints will still bring in a veteran for depth/insurance at that position
Problem is, as I recall the Saints drafted Ramcyzk with the idea of developing him into a right tackle, to take over for Zack Strief at some point. They will absolutely have to go out and find some veteran depth somewhere.