You think they want J. Rose doing this on 3rd and 9?
He plays off and gives the WR the first down, but watch his footwork right as the receiver is making his break. Rose takes a huge step backward, he's clearly afraid of getting beat over the top even though the receiver is still 3 yards in front of him. Rose can't recover from that terrible footwork. He could have easily challenged the receiver in press coverage and if he had any faith in his skills, should have played the man stride for stride and if the WR did go deep, you force the QB to make a tough throw over the top. Instead, it's a pitch and catch, no contact made by the DB on an easy 9 yard-out route.
I think the DB's think if they wave their hands in the "incomplete signal" that maybe it helps.