Both were injured in a Week 12 matchup with the Denver Broncos and have not practiced since. A timetable for their respective returns is not known.
With Dobson out, the Patriots might turn to veteran receiver Austin Collie, who was re-signed this week. In addition to Dobson, fellow rookie Kenbrell Thompkins (hip) is questionable and practicing on a limited basis this week.
Veteran Will Svitek is expected to earn his second consecutive start in Cannon's place. He's the third player to man the right side of the line for the Patriots this season, as season-opening starter Sebastian Vollmer was previously placed on injured reserve.
Cornerback Alfonzo Dennard (knee), who practiced Wednesday but was absent on Thursday and Friday to appear in court in Lincoln, Neb., for hearings relating to previous arrests, is among those players listed as questionable.