The 24-year-old, who was St. Louis' second-round pick in 2012, had his left knee buckle after a 33-yard kick return in the first quarter. He was helped off the field by team trainers and carted off the field.
Said Fisher: "It was just one of those non-contact, freak injuries that happen out there sometimes."
Pead, who suffered a fractured finger earlier in camp, was battling with rookie Tre Mason and Benny Cunningham for the team's backup running back spot behind Zac Stacy. He had 21 rushing yards, 78 receiving yards and 138 yards on five kick returns in 10 games last season.
- Chris Mascaro