Everyone is forgetting the new rules regarding Injured Reserve.
A few years ago teams could designate one player to be placed on Injured Reserve with a designation to return later in the season. That player had to be expected to miss six weeks (and do just that), and then after being activated to the 53-man roster still could not play for another two weeks but at that point being allowed to practice.
This year the rule has been amended so that teams do not have to designate a player prior to being placed on IR. A club could conceivably place two players on IR today and wait a month and a half to see how they are progressing, and then decide which player could return.
Right now the Patriots do not have any roster players on IR. Lewis, Vollmer and Flowers are all on Reserve/PUP. The Pats did not have to make a roster decision with Ninkovich and his injury since he was suspended.
Placing Garoppolo on Injured Reserve would be a wise decision in my opinion. Doing so would free up a valuable roster spot, and the time that he would have to sit neatly coincides with his injury rehab timetable.
The only downside is that should the Patriots go ahead and make this decision, then they cannot bring another player back on in-season IR this year. Hopefully that will not be an issue.