Porter missed practice Thursday to see a doctor and had been hoping to get medical clearance to play against his former team, but that clearance has not happened. He is officially listed as questionable for the game.
Porter, who had no history of seizures, wasn't allowed to fly to the Broncos' last game, at San Diego on Oct. 15, after he began experiencing light-headedness and a racing heart -- similar to the symptoms he felt before his seizure, team spokesman Patrick Smyth said.
Smyth emphasized that Porter did not suffer a second seizure but was left back in Denver as a precaution. Porter returned to practice on a limited basis this week.
Porter, whose seizure was first reported by The Denver Post on its website Thursday afternoon, wasn't in the locker room during the 45-minute media access period Thursday but later tweeted, "I would like to thank EVERYONE for the prayers and wishes. It really means a lot to me."
The last time Peyton Manning and Drew Brees squared off, in the 2010 Super Bowl, it was Porter who stole the spotlight, returning an interception 74 yards to seal the Saints' 31-17 win over the Indianapolis Colts.
Porter had sidestepped questions about the nature of his illness earlier this week.
Information from The Associated Press was used in this report.