It’s December, a time for contenders to emerge and pretenders to fade away. So go ahead and try explain what happened this past Sunday in the NFL. The Detroit Lions beat the Minnesota Vikings, who came in at 10-2. The Jacksonville Jaguars beat the division-leading Tennessee Titans and the Carolina Panthers went on the road to beat the Seattle Seahawks, a team that appeared to be surging to the postseason. Detroit, Jacksonville and Carolina are all alive in the playoff chase. In December? Can it be? The Lions have won five of six to get to 6-7 and get within a game and a half of being in the playoff…