Eight in the Box: Can't-lose players

Other than the quarterback, which player could each NFC North team least afford to lose to injury? Here’s a look:

Chicago Bears: DE Julius Peppers. Peppers has been more responsible than any player for the rejuvenation of the Bears' defense since his arrival in 2010. Over that span, he has drawn top priority from opposing offenses but still managed to record 30.5 sacks and force seven fumbles. There is no substitute for a dominant pass-rusher. Perhaps most importantly, he has played through knee and other injuries to start all 48 regular-season games since the Bears signed him to a $64 million contract. It's no coincidence that defensive tackle Henry Melton has emerged to record 15.5 sacks over the same period. Without Peppers, the Bears wouldn't have a front-line player who can perform while drawing high attention from opponents.

Detroit Lions: WR Calvin Johnson. The offense would look much different without Johnson's freakish attributes. Did you realize that Johnson caught 122 passes for an NFL-record 1,964 yards in 2012 even while the Lions faced more pass-stacked sets than any other team? Imagine what he could do if defenses were forced to play honest. We have long known that there are no other NFL receivers with Johnson's combination of strength, size and ball skills. But he has brought it all together in recent years to be just as important to his team as quarterback Matthew Stafford.

Green Bay Packers: LB Clay Matthews. As is the case with Peppers, there is no substitute for a dominant pass-rusher, and Matthews has the fifth-most sacks in the NFL since his arrival in 2009. He has occasionally been limited by leg injuries, and it has been notable to track the impact of his absence -- and not just on the Packers' pass defense. Last season, in the four games Matthews missed because of a hamstring injury, opponents averaged 5.5 yards per carry against the Packers. In the first two games after he returned, that average was 3.38 yards per carry. Like Peppers, Matthews give the Packers' defense a schematic foundation that few other players could achieve.

Minnesota Vikings: RB Adrian Peterson. Let's not overthink this one. Last season, Peterson nearly broke the NFL record for rushing yards in a season. His final regular-season carry got the Vikings in position for a chip-shot field goal to clinch the playoffs. And in the three games that quarterback Christian Ponder failed to eclipse 100 yards passing, Peterson compensated with 489 rushing yards. The Vikings have built their entire offense around Peterson since Leslie Frazier took over as the their permanent coach in 2011. Peterson is the most important non-quarterback in the NFL.