Without providing any specifics of the injury, coach Chan Gailey said "it doesn't look good." Based on the initial prognosis, Gailey added that there is a question as to whether Nelson will recover in time for the Bills' season opener against the Miami Dolphins on Sept. 12.
Nelson was hurt about an hour into practice while taking part in a team red zone drill. Making a catch over the middle from Levi Brown, Nelson turned toward the end zone and was on his way down when he was nudged sideways by a defender, who was attempting to stop himself from making a collision.
It appeared that Nelson's right foot got caught in the turf as he fell.
Nelson immediately clutched at his lower leg. Trainers spent about five minutes treating the player and keeping his foot elevated. Nelson was then loaded into a cart and unable to put any weight on his foot.
An undrafted rookie free agent out of Florida, Nelson is part of a raw and inexperienced receiving corps competing for a backup spot on the team.
He had a solid NFL debut, making a team-high five catches for 47 yards and a touchdown in a preseason-opening 42-17 loss at Washington last week.
Buffalo is already down two receivers entering its preseason game against the Indianapolis Colts on Thursday at Toronto. Rookie Marcus Easley is set to have surgery on his left knee, and James Hardy has missed a week with an undisclosed injury.
And that doesn't include Felton Huggins, who was waived/injured last week after he hurt his left shoulder.
Starting free safety Jairus Byrd missed practice Tuesday because of what Gailey would only refer to a "physical complication." Gailey provided no other details except to say he believes it will be resolved very quickly and that the player was having the complication checked out.