Sports Stats ‘on Tapp’ is a sports statistics blog published with a focus on stats that go beyond the numbers.

Heading into the last four weeks of the NFL regular season, four teams have stopped their opponents’ offenses from scoring in 70 percent or more of their possessions. Topping the list is the San Francisco 49ers defense, which has 94 stops in 129 possessions, a 74.6 STOP Factor.

The other three teams are: Houston (74.0 percent), Chicago (73.0 percent) and Arizona (72.2 percent). This is the third consecutive week that the 49ers defense has held the number one spot in these rankings.

If we look at the rankings after Week 9, we see that several teams have amped up their defensive efforts in the last month while others have seen their defenses drop in the rankings. The biggest gainers since Week 9 have been the Cincinnati Bengals who have jumped from 22nd in the rankings to a Top 10 spot at number 10, a gain of 12 spots. The Denver Broncos have jumped from 14th to sixth (a move of eight posts), and the Pittsburgh Steelers have gone from 18th four weeks ago to 11th this past week.

Two teams, Miami and Philadelphia, have seen the biggest drops in their rankings in the last four weeks. Miami has gone from seventh to 14th, while the Eagles have dropped from 17th to 24th, both a loss of seven spots.

(The STOP Factor is based on the premise that it is the defense’s job to stop their opponents from scoring on each possession. To get a team’s STOP Factor, you divide the number of times a defense stops the offense from scoring – offensive unit TD or field goal – by the number of total possessions by the opposition.)

Following is each NFL teams’ STOP Factor. Listed is how many times each team stopped the opponents from scoring, the number of possessions their opponents had, and the percentage of possessions that each team prevented the other team from scoring (stats are through Week 13 games).

Team, Opponents’ scoreless possessions/opponents’ possessions, STOP percentage

1. San Francisco 74.6 (94 stops in 126 possessions)

2. Houston 74.0 (111 stops in 150 possessions)

3. Chicago 73.0 (103 stops in 141 possessions)

4. Arizona 72.2 (104 stops in 144 possessions)

5. Seattle 69.7 (83 stops in 119 possessions)

6. Denver 69.1 (96 stops in 139 possessions)

7. Cleveland 69.0 (98 stops in 142 possessions)

8. Atlanta 67.2 (86 stops in 128 possessions)

9. Tampa Bay 66.7 (90 stops in 135 possessions)

10. Cincinnati 66.4 (87 stops in 131 possessions)

11tie. Pittsburgh 66.1 (82 stops in 124 possessions)

11tie. San Diego 66.1 (84 stops in 127 possessions)

13. New England 65.4 (87 stops in 133 possessions)

14. Miami 65.2 (88 stops in 135 possessions)

15. Green Bay 64.7 (86 stops in 133 possessions)

16. New York Giants 64.2 (79 stops in 123 possessions)

17. Baltimore 64.0 (89 stops in 139 possessions)

18. New York Jets 63.9 (85 stops in 133 possessions)

19. St. Louis 63.8 (83 stops in 130 possessions)

20. Detroit 62.7 (84 stops in 134 possessions)

21. Minnesota 61.8 (81 stops in 131 possessions)

22. Dallas 59.8 (73 stops in 122 possessions)

23. Indianapolis 59.4 (76 stops in 128 possessions)

24. Philadelphia 58.7 (74 stops in 126 possessions)

25. Washington 58.0 (76 stops in 131 possessions)

26. Buffalo 57.8 (74 stops in 128 possessions)

27. New Orleans 57.6 (76 stops in 132 possessions)

28. Kansas City 57.0 (69 stops in 121 possessions)

29. Tennessee 55.7 (73 stops in 131 possessions)

30. Jacksonville 54.5 (73 stops in 134 possessions)

31. Carolina 53.2 (66 stops in 124 possessions)

32. Oakland 51.9 (70 stops in 135 possessions)

Biggest gainers this week: Cincinnati (up three spots this week); New York Jets (up three spots this week).

Biggest losers this week: Miami (down five spots this week); Minnesota (down three spots this week); San Diego (down three spts this week)

Average league STOP Factor (through Week 13): 63.7

Follow Jerry on Twitter @StatsonTapp