The Minnesota Vikings probably fielded the National Football League's worst defense in 2013. They were the worst in terms of points allowed, becoming just the eighth team since the merger to allow 30 points/game, and they were second-to-last in yards allowed at 397.6 yards/game. Only the Dallas Cowboys were worse in that second category.
There was another area where the Minnesota defense was particularly bad last season, and that was in allowing "splash plays," or plays of 20 yards or more. According to Jimmy Kempski on Twitter (who used to be the head blogger for our friends at Bleeding Green Nation), the Vikings allowed 71 "splash" plays in 2013. There were six teams that were worse in that regard, with the Cowboys and Jacksonville Jaguars tying for the league lead with 79 of those plays allowed.
Of the 71 "splash" plays that the Vikings allowed in 2013, a whopping 57 of them came via the pass. Some of this might be the scheme the Vikings were running last year, and some of it could be chalked up to talent (particularly the loss of Harrison Smith for most of the season).
Over in Cincinnati, on the other hand, the Bengals defense was very stingy when it came to allowing big plays. Mike Zimmer's defense allowed a total of 42 "splash" plays in 2013, the second-lowest total in the NFL. Only the Seattle Seahawks allowed fewer (36). Of the Bengals' 42 big plays allowed, 36 of them came in the passing game, while they only allowed six runs of longer than 20 yards all season.
We've seen the Vikings upgrade their defensive personnel over this off-season, with the additions of Linval Joseph and Captain Munnerlyn, among others. Hopefully with the new attitude and updated scheme that Mike Zimmer will be bringing to Minnesota, the Vikings will be making more big plays on defense and giving up less of them. Both of those things could go a long way in getting back to the top of the NFC North.