I'm hoping not to turn this site into 4thDownAnalysis.com, but I did get several requests to look at another controversial 4th down decision. (And I'll always be happy to take requests.) Down 14-13 to DET, CHI faced a 4th and goal from the 1 with about 9 minutes left in the 4th quarter. A FG is nearly automatic, giveing CHI a 2-point lead and a 0.59 WP.
Conversion attempts from the 1 are successful about 68% of the time. A successful TD gives CHI a 6-point lead and a 0.79 WP. A failed attempt leaves DET at its own 1, but with a 1-point lead, worth 0.44 WP for CHI. On net, the conversion attempt is worth 0.68*0.79 + (1-0.68)*0.44 = 0.68 WP. Going for it was the right call by a large margin--0.68 to 0.59.
CHI went for it, but Matt Forte was stopped for no gain. But that's only half the story.
The bigger blunder was the next 4th down. With 4:24 left in the game, still down by 1, CHI punted on 4th and 4 from the...DET 38! DET took possession at their own 14, for a net punt distance of a whopping 24 yards.
The punt left CHI with a 0.26 WP. A 4th and 4 conversion in that region of the field is successful about 55% of the time. A success is worth 0.65 WP, while a failed attempt is worth 0.31 WP to CHI. On net, we have 0.55*0.65 + (1-0.55)*0.31 = 0.50 WP. This was a monumental blunder, costing CHI 0.24 WPA. Imagine, a single strategic decision costing a team a quarter of a win.
Many coaches these days will go for it on 4th and 4 from the opponent's 38 regularly, simply because kicking is pretty worthless in that spot. But to kick in that situation while losing by a single point, with time dwindling in the 4th quarter, is pretty amazing. Think of all the things that had to go CHI's way for them to win: they keep DET from running out the clock or scoring, then drive most of the field, just to get back to where they were on 4th and 4 at the 38. Although 55% is far from automatic, converting a simple 1st and 10 is just a 67% proposition. Besides, even if the attempt fails, CHI still have all the same options you had if they had punted, minus 24 yards of field position.
You have to think that the failure to score on the previous 4th down was probably in the back of Lovie's head when he punted there.
As luck would have it, CHI pulled out the win. But that was in-part thanks to a freakish (although technically correct) DET incompletion in the end zone at the end of the game.