Strength of schedule, the combined winning percentage of future opponents, is the most relative statistic imaginable -- especially in the first half of an NFL season. It changes weekly, the numbers fluctuate wildly and it serves only as an estimate of a team's future at a moment in time.

With those caveats in mind, the current SOS standings struck me this week while researching the Inside Slant podcast with Mike Sando. NFC North teams have two of the top three most-difficult schedules for the remaining 11 weeks of the season, according to the Elias Sports Bureau, and all four rank in the top 10.

There are some obvious explanations for the rankings, including this season's matchup with the NFC West, which currently houses a trio of 4-2 teams. The AFC South, another matchup for our division, boasts the 5-1 Houston Texans. And let's not forget we play against each other as well; we currently have a pair of four-victory teams in the Chicago Bears and Minnesota Vikings.

So it's not surprising that the Detroit Lions have the NFL's most difficult schedule moving forward, based on current records. They have two games remaining against the Bears, and one against the Seattle Seahawks (4-2), the Vikings (4-2), the Texans, Arizona Cardinals (4-2) and Atlanta Falcons (6-0).

The Vikings, meanwhile, rank two spots below the Lions mostly because they will play the Tampa Bay Buccaneers (2-3) instead of the Falcons.

What's scary for both teams is that the Green Bay Packers, at 3-3, aren't really moving the strength of schedule needle at the moment, but figure to be a formidable opponent moving forward. The Lions and Vikings each have two games remaining against them.

Again, I've never thought strength of schedule should be a guidebook to a team's season. It's part of a bigger picture, and our aim is to bring you as many of the parts as we can. Or something like that.