New Orleans Saints rookie defensive back Kool-Aid McKinstry suffered an apparent injury during the team’s opening series of a preseason game against the San Francisco 49ers. McKinstry was in coverage on a third down when 49ers quarterback Brock Purdy was pressured in the pocket. Purdy released a throw and a receiver in the area panicked and attempted to tackle Kool-Aid McKinstry, who was in the vicinity of the throw. McKinstry slipped the tackle attempt but came up limping, seemingly favoring his hamstring. He then went into the injury tent on the sideline. He stayed there with trainers for a …