Everyone has talked about Riverboat Ron and his newfound willingness to go for it in fourth down situations. But that is only part of the story.
I can't find the quote, but I remember Rivera had a quote after the Bears loss last year, (paraphrasing) "You have to make them drive down the field and beat you". and one of the beat writers writing "That is exactly what they did"
Time after time, we would get in these situations and we would run very basic coverage, just keep everything in front of you, just rush 3 or 4, drop 7 or 8, get really deep, etc.
But in these late game situations during this win streak, he has also gambled much more often on defense late in games, and it has paid off big time. Against New England only up by 4 we dialed up a CB blitz on that final drive, against SF Kuechly blitzed one of their final drives and got a sack, if I recall Mitchell got a sack late in the game against the Rams.
No longer, late in games in crucial defensive positions are we just sitting back and hoping they make a mistake. Riverboat Ron has gotten much more aggressive and has shown much more faith in the defense to make a play and cover with sending extra guys and being aggressive on the perimeter instead of just loose zones and being conservative.
I think the change has also played as much of a part in our winning streak and ability to win close games as has his willingness to go for it on fourth down.