Here's a look at a key matchup heading into Sunday's Vikings-Patriots game in Foxborough:
Vikings nickel offense vs. Patriots' third-down defense
Any matchup for this game must include the caveat that Brett Favre is injured, but this was written under the auspice that Favre plays. Why? He always plays.
The Vikings have had their share of ills offensively, this season, but they are getting better on third downs. After Sunday's 6-for-14 conversion rate on third downs, they now are converting 40.5 percent on the season, just over the league average of 38.4. And despite Favre's troubles this season, there is enough firepower on offense to make big plays after the catch.
Look for Percy Harvin to be a key figure in this matchup. Opposing slot receivers have led the team in receiving in the Patriots' past four games, and Harvin has been coming on. He has been used in a variety of ways — split wide, in motion, out of the backfield — but the slot is likely where he'll see a high number of plays.
Who the Patriots pick to defend him is anyone's guess. They have used a three-safety alignment at times in their nickel defense, though that remains to be seen for this weekend with Patrick Chung and Jarrad Page battling injuries. Jonathan Wilhite has been used as a slot corner, but he hasn't been heard from much recently. Kyle Arrington has vaulted up the depth chart, but he mainly plays outside, as does Darius Butler, who has been pushed down the chain and almost out of the picture of late. The Patriots have been a zone-heavy team, which would make a lot of sense against Harvin and Randy Moss.
But there's always the Favre factor or — if he plays — the Tarvaris Jackson factor. Favre has struggled badly against the blitz this season (50 percent completions, two TDs, five INTs), and Jackson has struggled badly against additional pressure in the past. The Patriots could opt to blitz a defensive back from their nickel package on third downs as a way to jump start what is the worst unit statistically (48.8 conversion percentage allowed on third downs) in the NFL.