But receiver Stevie Johnson is considered probable.
That was the update coach Chan Gailey provided on the status of several injured players who returned to practice Monday, a day after the team got a day off from training camp in suburban Rochester.
"I would say that we won't push David, we won't push Eric," Gailey said.
Nelson was limited to participating in individual drills on Monday in his first practice since spraining his right knee on July 28, three days into training camp. Wood has been getting more practice time in team sessions, but Gailey doesn't want to risk rushing the player who is coming off a season-ending knee surgery.
Gailey wasn't certain on the status of veteran cornerback Terrence McGee, who has been practicing on a limited basis while also recovering from season-ending knee surgery.
On the bright side, Johnson showed little signs of a groin injury that had been nagging him the previous two practices. Barring setbacks, Gailey expects Johnson to play.
Gailey also had a positive update on the status of offensive tackle Eric Pears, who has been out since the second day of training camp after aggravating a groin injury. Pears had what Gailey described as a good visit with a specialist, who has provided the player some advice on how to deal with the injury.
Looking ahead to his plans for the game, Gailey expects to limit his starters to between 15 and 18 plays.
The Bills also announced there are more than 20,000 tickets still available, which means the game will be blacked out on local television.