Reiff, who had his right leg/knee rolled up on in the team's preseason finale Aug. 25, was a top candidate to be the team's No. 1 right tackle. Being placed on injured reserve means Reiff will miss at least the first four games of the season.
Injuries, illness and inconsistency along the offensive line has been one of the top storylines of Patriots camp, which led the team to keep an NFL-high 11 offensive linemen on its initial 53-man roster.
Starting quarterback Mac Jones took some big hits in the team's second preseason game behind a patchwork line that has been buying time until starting guards Cole Strange (left leg/knee) and Mike Onwenu (offseason ankle surgery) -- who have missed the majority of training camp -- return to full health.
Five-year veteran Calvin Anderson is a top option to replace Reiff at right tackle, while recent trade acquisitions Tyrone Wheatley Jr. and Vederian Lowe are among other possibilities. Right guard Onwenu also has experience at right tackle.
Anderson was activated off the non-football illness list late last week, which along with the trades for Wheatley and Lowe led coach Bill Belichick to say Monday: "We gained three tackles there in one day it seemed like, and it was good to get that."
The Patriots signed tight end Pharaoh Brown from their practice squad to fill Reiff's spot on the 53-man roster.