You can't always count on turnovers. That's true, but I think what we have is Marvin knowing the strengths and weaknesses of the defensive personnel he has at his disposal and coaching them to emphasize the strengths in an effort to make up for the weak areas. This isn't a team that can flat out shut down the run and be in the QB's face all day long, so they emphasize trying to force turnovers. They're not going to force opposing offences into 3 and out possessions all day long. The turnover is their bread and butter right now. You get a good run stuffing DL in there that can give you a decent pass rush, and this would be one of the best defenses in the league.