The reason for Brady's absence is unclear, as is whether he will take part in any portion of Wednesday's practice. A source told ESPNBoston.com's Mike Reiss that Brady is "good and will be ready for Sunday."
Brady did not suffer any apparent injury during the team's game against the Colts on Saturday night, though he was sick throughout the week last week.
He has been listed as a limited participant with a shoulder injury on multiple occasions since late October, though Brady has not missed a practice this season.
The Patriots moved Brady's regularly scheduled Wednesday news conference to Friday morning.
He was one of two Patriots not seen at the start of practice, as long snapper Danny Aiken, who was also playing through illness on Saturday night, was also not spotted.
Meanwhile, the Patriots did have punter Ryan Allen, who left Saturday's game with a shoulder injury, on the field. Allen suffered an AC sprain, according to sources, and the team is hopeful he can rehab the injury this week to a point that he is good to go on Sunday.
Finally, wide receiver Aaron Dobson, who was injured in Week 17 and had not practiced since that time, returned to practice on Wednesday as he continues to work through a foot injury.