So I've spent some of this offseason downtime fiddling with the vast database of ESPN Stats & Information. Now that I'm more familiar with "filter," "sort" and other research tools, I'm hoping to provide additional focused insight into how and why things happen in the NFC North.

First up is what I guess we should call "The Calvin Johnson Effect," although I think it's probably more complicated than that. In either event, the database reveals how dramatically defenses altered their standard approach against the Lions in 2012. It also illustrates how limited the Lions' running game was in exploiting those schemes, and highlights the challenges Johnson faced in breaking the NFL record for yards in a season.

In 2012, the Lions ran more plays (855 of a possible 1,160) against defenses with six or fewer defenders in the box than any other team. They also faced, by far, the fewest number of "stacked" boxes -- eight or more defenders within two yards of the tackle and five yards deep. That happened on only 1.6 percent of their plays (19 of 1,160).

(The Lions saw a "standard" look -- seven defenders in the box -- on 286 plays, the third-fewest in the league.)

That's an understandable split when facing a team with the NFL's best receiver and one of its least-threatening running games. A six-man box is an open invitation to run, and to their credit, the Lions tried. In 231 attempts, they rushed for an average of 4.48 yards per carry and scored four touchdowns. But they managed a first down on only 18.6 percent of those runs, tied for No. 21 in the NFL in that scenario, which to me is a bottom-line percentage that opposing defenses can live with in exchange for maximum attention on Johnson.

Now let's turn the numbers around. By definition, Johnson did most of his damage in 2012 against pass-stacked defenses. With six or fewer defenders in the box, and thus five or more in coverage, Johnson caught 91 of his 122 passes for 1,428 of his 1,964 yards and all five of his touchdowns.

What does this mean as the Lions begin constructing their team for 2013? I think it highlights the need for a running back/running scheme that can better capitalize on defenses who are dropping one or more extra defenders into coverage as frequently as they did against the Lions last season. Perhaps Jahvid Best could have filled that role, and it's one we've discussed in relation to free agent Reggie Bush as well.

Regardless, there is a world of untapped first downs available for the Lions via their running game as long as Johnson is in his prime. Let's see if they can capitalize better in 2013.