Brady was seen out on the field during the part of the session available to media but was listed by the team as a non-participant. As noted by Mike Reiss of ESPN.com, Brady was wearing a glove on his throwing hand—something that is not standard practice for the MVP favorite.
The team has not gone into detail about the nature of Brady's injury. A press conference with Brady scheduled for Thursday was moved to Friday, the same day league rules mandate the Patriots release an injury report.
The sports injury expert for the San Diego Union-Tribune said it's "likely" Brady suffered a dislocation of a finger on his throwing hand. Based on the nature of the reporting, the doctor said the dislocation likely caused a laceration to the skin on Brady's finger.
All of this is speculative, and we'll know more of the nature of Brady's injury as we get closer to Sunday's kickoff.
However, any injury—whether it keeps him out of the lineup or not—will only increase the odds of the Jaguars pulling off an improbable upset. The Patriots traded backup Jimmy Garoppolo to the San Francisco 49ers during the regular season, leaving them with only Brian Hoyer as a potential replacement if Brady is out of the lineup.
The Jaguars already posed a formidable threat with their swarming defense, which gets consistent pressure on quarterbacks without the need of intricate blitz systems. Add in Brady's injury, and an upset doesn't seem as unlikely as it did a week ago.