The rookie running back ruptured his left Achilles tendon and will undergo season-ending surgery on Tuesday.
Brown was hurt running a pass pattern down the right side of the field near the end of Friday evening's workout. Brown jumped to catch a pass thrown by Andre' Woodson but crumpled to the ground and instantly grabbed his left leg. Brown appeared to suffer the injury as he went up for the ball.
Brown, from North Carolina State, had played well in training camp – he scored a touchdown in a goal line drill on Wednesday – and was expected to see his first NFL action in the preseason opener on Monday night against the Carolina Panthers.
As Brown was being examined on the ground, he pounded his fist into the ground two or three times. Brandon Jacobs and some other players ran over to check on him, as did head coach Tom Coughlin. Brown was lifted onto a cart and driven off as he pulled his jersey over his face.