As mentioned above, Mathews leads the NFL with 534 rushing yards in the month of December and has three 100 yard games and 3 TDs in December as well. Lucky for the Bengals
1) it is no longer December
2) 4 of the 5 games were in SD
3) 4 of the 5 games were against terrible defenses (Oak, NYG, Den, KC)
4) his lowest total of the month (61) came against the Bengals. Along with Mathews, the Chargers also have Woodhead who lead all running backs with 76 receptions. Between Mathews and Woodhead, the Chargers backfield has accounted for nearly 2,500 all-purpose yards and 15 TDs.
While the Bengals also have a pretty serviceable duo of their own, the Bengals duo averages .6 YPC less than the Chargers duo and they trail the Chargers duo by more than 500 all-purpose yards. I don’t see this as a big edge, but I give the Chargers a slight edge here.