Oklahoma claims a top-four spot in CFB Power Rankings after Week 13

Oklahoma moves into the top four of SI.com's college football power rankings after week 13.

The 2015 regular season is in the books, so let’s take a quick look back before championship Saturday settles the College Football Playoff picture.

Only four teams held the No. 1 spot this season. Ohio State started with it before Michigan State took over. Utah claimed the top ranking after Week 4, but the Utes’ Week 8 loss to USC allowed Clemson to move up. The Tigers have held it ever since.

Among teams in the current top four, Iowa began the season unranked and didn’t enter the top 25 until after Week 5. Oklahoma dropped to No. 20 after its loss to Texas before climbing back into the playoff field. When Alabama fell to Ole Miss and followed that up with a shaky offensive performance against Louisiana-Monroe, the Crimson Tide sunk to No. 14. And Clemson bottomed at No. 13 before its victory over Notre Dame shot it back up.

A lot changes over the course of 13 weeks, as the path of each of the top four teams illustrates. That’s what makes this fun.

1. Clemson Tigers

PREVIOUS: 1

RECORD: 12-0

Last week: Beat South Carolina 37-32Next week: Saturday vs. North Carolina

2. Alabama Crimson Tide

PREVIOUS: 2

RECORD: 11-1

Last week: Beat Auburn 29-13Next week: Saturday vs. Florida

3. Oklahoma Sooners

PREVIOUS: 6

RECORD: 11-1

Last week: Beat Oklahoma State 58-23Next week: No game

4. Iowa Hawkeyes

PREVIOUS: 3

RECORD: 12-0

Last week: Beat Nebraska 28-20Next week: Saturday vs. Michigan State

5. Michigan State Spartans

PREVIOUS: 4

RECORD: 11-1

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6. Ohio State Buckeyes

PREVIOUS: 9

RECORD: 11-1

Last week: Beat Michigan 42-13 Next week: No game

7. Stanford Cardinal

PREVIOUS: 13

RECORD: 10-2

Last week: Beat Notre Dame 38-36Next week: Saturday vs. USC

8. Notre Dame Fighting Irish

PREVIOUS: 5

RECORD: 10-2

Last week: Lost to Stanford 38-36 Next week: No game

9. TCU Horned Frogs

PREVIOUS: 16

RECORD: 10-2

Last week: Beat Baylor 28-21 in 2OT Next week: No game

10. Baylor Bears

PREVIOUS: 7

RECORD: 10-2

• Oklahoma proves ready for playoff

11. North Carolina Tar Heels

PREVIOUS: 12

RECORD: 11-1

Last week: Beat North Carolina State 45-34 Next week: Saturday vs. Clemson

12. Oklahoma State Cowboys

PREVIOUS: 8

RECORD: 10-2

Last week: Lost to Oklahoma 58-23 Next week: No game

13. Northwestern Wildcats

PREVIOUS: 14

RECORD: 10-2

Last week: Beat Illinois 24-14 Next week: No game

14. Florida State Seminoles

PREVIOUS: 17

RECORD: 10-2

Last week: Beat Florida 27-2 Next week: No game

15. Florida Gators

PREVIOUS: 10

RECORD: 10-2

• Bama has bigger goals after Iron Bowl

16. Ole Miss Rebels

PREVIOUS: 19

RECORD: 9-3

Last week: Beat Mississippi State 38-27 Next week: No game

17. Oregon Ducks

PREVIOUS: 18

RECORD: 9-3

Last week: Beat Oregon State 52-42 Next week: No game

18. Houston Cougars

PREVIOUS: 21

RECORD: 11-1

Last week: Beat Navy 52-31 Next week: Saturday vs. Temple

19. Michigan Wolverines

PREVIOUS: 11

RECORD: 9-3

Last week: Lost to Ohio State 42-13 Next week: No game

20. Temple Owls

PREVIOUS: 22

RECORD: 10-2

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21. Navy Midshipmen

PREVIOUS: 15

RECORD: 9-2

Last week: Lost to Houston 52-31 Next week: No game

22. LSU Tigers

PREVIOUS: 23

RECORD: 8-3

Last week: Beat Texas A&M 19-7 Next week: No game

23. Utah Utes

RECORD: 9-3

Last week: Beat Colorado 20-14 Next week: No game

24. Wisconsin Badgers

RECORD: 9-3

Last week: Beat Minnesota 31-21 Next week: No game

25. Memphis Tigers

RECORD: 9-3

Last week: Beat SMU 63-0 Next week: No game

Dropped out: Toledo, Washington State, UCLA
Next five: USC, Georgia, Toledo, Western Kentucky, UCLA