The Lab CFB ratings movers, week 9: USC beats Ohio State, and Georgia is the new number 1
CFB ratings movers, week 9: USC beats Ohio State, and Georgia is the new number 1
After week 9, USC's 30 to 18 win over Ohio State moved USC from 34th to 18th in our college football rating and Ohio State from 1st to 5th, Georgia took over number 1, and Sacramento State had the biggest gain yet stayed 138th. Each move below is traced to the game and the margin our number expected.
USC beat Ohio State 30 to 18 at home in week 9, and Georgia is now number 1 in our rating. Our rating expected Ohio State to win by about 12.95, so USC’s 12 point win was a miss of 24.951 points. USC gained 2.935 and moved from 34th to 18th, while Ohio State lost 3.119 and fell from 1st to 5th. Georgia beat Florida 27 to 8 at a neutral site, gained 0.820, and moved from 2nd to 1st. LSU and Alabama were idle and moved up to 2nd and 3rd without playing. Ole Miss beat Auburn 45 to 15 and rose from 7th to 4th. UCF had the biggest drop, 22 spots, after losing 41 to 9 to Baylor, and Jacksonville State the biggest climb, 20 spots.
Every rating, rank, expected margin and move here is from our in-season CFB rating, the weekly update layer on top of each team’s preseason number. The week 9 rows were written after the week’s finals, and each team’s entering rating below equals its week 8 row, which we checked for all 138 teams. “Rank” always means rank in our rating across the 138 FBS teams we rate, not any poll. Figures are rounded from stored values. A rating and its move are each rounded to three decimals on their own, so a week 8 rating plus its move can miss the week 9 rating by 0.001.
How a move is computed
Each team’s rating moves by one number: a weight times its error. The error is the game’s margin, capped at 28, minus the margin our ratings expected. The expected margin is the team’s rating minus its opponent’s, plus 2.5 points for home field, minus 2.5 on the road, and nothing at a neutral site. The weight shrinks as the season goes on.
Worked example, USC at home against Ohio State:
- Expected margin: USC’s entering rating of 8.445 minus Ohio State’s 23.896 is minus 15.451. USC was at home, so add 2.5, for minus 12.951. Our rating had Ohio State winning by about 13.
- Actual margin: USC 30, Ohio State 18, so plus 12. That is under the cap of 28, so it counts in full.
- Error: 12 minus minus 12.951 is 24.951.
- Weight: USC’s weight for this game was 2/17, or 0.1176.
- Move: 24.951 times 2/17 is 2.935 rating points.
Ohio State, on the other side of the same game, had a weight of 2/16, or 0.125. Its error was minus 24.951, and 24.951 times 2/16 is a loss of 3.119, a little larger than USC’s gain because Ohio State’s weight was heavier.
That weight comes from setting the preseason prior to be worth about eight games of evidence. We walk through that choice in the preseason prior is worth eight games. Two consequences matter for this week. Each team’s weight depends on how many games it has already played: 95 teams carried 2/16 and 17 carried 2/17. The other 26 teams were idle. And nothing past 28 points counts, even when the opponent was supposed to be much worse.
Why a loss can raise a rating
Northern Illinois is the clean case. It lost 31 to 24 at UNLV, a margin of -7, and its rating went up 2.195. Our rating expected UNLV to win by about 24.6: Northern Illinois’s entering minus 23.433 minus UNLV’s minus 1.372 is minus 22.061, and Northern Illinois’s road game takes it to minus 24.561. The error is minus 7 minus minus 24.561, which is 17.561, and 2/16 of that is +2.195. Northern Illinois went from a rating of minus 23.433 to minus 21.238 and stayed 137th. UNLV, with the same weight, lost the same 2.195 for the win and fell from 75th to 84th.
It was not the only one. North Carolina lost 38 to 35 at home to Miami, a margin of -3 against an expected minus 14.71, and gained 1.464. Miami’s road win cost it 1.464 and dropped it from 5th to 8th. Across the week, 12 teams lost and still gained rating points, and 12 won and lost them. Notre Dame was one of those 12: it beat Navy 35 to 13 at a neutral site, a margin of 22 against an expected 23.92, and lost 0.241. No team in a rated game played an FCS opponent this week, so the minus 22 we pin on FCS teams did not enter any move.
None of that is a verdict on the games. With UNLV expected by 24.6, a 7 point loss on the road beat the expectation by 17.6 points, and beating the expectation is what moves the number up.
Biggest risers
Margin and expected margin are from the team’s side. “Site” is home or road for the risers and fallers, taken from the game results.
| Team | Our rank, wk 8 to wk 9 | Rating change | Opponent | Site | Margin | Expected |
|---|---|---|---|---|---|---|
| Sacramento State | 138 to 138 | +3.685 | Kent State | Home | +21 | -10.32 |
| Baylor | 41 to 30 | +3.431 | UCF | Road | +32 (counts as 28) | +0.56 |
| Iowa | 27 to 15 | +3.069 | Wisconsin | Home | +30 (counts as 28) | +3.45 |
| Memphis | 60 to 47 | +3.028 | Army | Home | +27 | +1.26 |
| Jacksonville State | 106 to 86 | +2.999 | New Mexico State | Road | +24 | +0.01 |
| USC | 34 to 18 | +2.935 | Ohio State | Home | +12 | -12.95 |
| Troy | 121 to 107 | +2.879 | James Madison | Road | +3 | -20.03 |
| Kennesaw State | 129 to 121 | +2.666 | Middle Tennessee | Road | +16 | -5.33 |
Sacramento State had the largest single gain of the week, and it is still 138th of 138. Its 31 to 10 home win over Kent State came when our rating expected Kent State by 10.32, a miss of 31.324 points, and lifted it from minus 25.402 to minus 21.717. Northern Illinois, at minus 21.238, is the team just above it. Iowa beat Wisconsin 30 to 0 at home, a margin of 30 that counted as 28, and moved up 12 spots. Jacksonville State won 24 to 0 at New Mexico State and moved up 20 spots, the most of any team.
Biggest fallers
Every faller is the other side of a riser’s game.
| Team | Our rank, wk 8 to wk 9 | Rating change | Opponent | Site | Margin | Expected |
|---|---|---|---|---|---|---|
| Kent State | 127 to 131 | -3.685 | Sacramento State | Road | -21 | +10.32 |
| UCF | 53 to 75 | -3.431 | Baylor | Home | -32 (counts as -28) | -0.56 |
| Wisconsin | 31 to 38 | -3.069 | Iowa | Road | -30 (counts as -28) | -3.45 |
| Army | 51 to 69 | -3.217 | Memphis | Road | -27 | -1.26 |
| New Mexico State | 114 to 127 | -2.999 | Jacksonville State | Home | -24 | -0.01 |
| Ohio State | 1 to 5 | -3.119 | USC | Road | -12 | +12.95 |
| James Madison | 37 to 49 | -2.709 | Troy | Home | -3 | +20.03 |
| Middle Tennessee | 117 to 128 | -2.666 | Kennesaw State | Home | -16 | +5.33 |
UCF’s 22 spot drop was the biggest of the week. Baylor won 41 to 9 at UCF, a margin of 32 that counted as 28, against an expected 0.56. Army fell 18 spots after losing 49 to 22 at Memphis.
Each game pairs the two teams, but each side moves by its own weight, so the two moves match only when both teams have the same weight. Three of these eight pairs do not match. Memphis gained 3.028 at 2/17 while Army lost 3.217 at 2/16. USC gained 2.935 at 2/17 while Ohio State lost 3.119 at 2/16. Troy gained 2.879 at 2/16 while James Madison lost 2.709 at 2/17. In each case the heavier weight went to the team with fewer games played.
The top 10 after week 9
Georgia is number 1 in our rating, at 23.797, up 0.820 from 22.977. LSU is second at 22.317 and Alabama third at 21.598. Both were idle, so neither rating moved, and they rose a spot each because Ohio State dropped out of the top spot. Georgia leads LSU by 1.480.
| Rank | Team | Rating | Change from week 8 | Rank last week |
|---|---|---|---|---|
| 1 | Georgia | 23.797 | +0.820 | 2 |
| 2 | LSU | 22.317 | 0.000 | 3 |
| 3 | Alabama | 21.598 | 0.000 | 4 |
| 4 | Ole Miss | 21.047 | +2.175 | 7 |
| 5 | Ohio State | 20.777 | -3.119 | 1 |
| 6 | Texas | 19.893 | +1.672 | 8 |
| 7 | Notre Dame | 18.953 | -0.241 | 6 |
| 8 | Miami | 18.944 | -1.464 | 5 |
| 9 | Tennessee | 16.484 | 0.000 | 10 |
| 10 | Indiana | 15.923 | -1.277 | 9 |
Georgia’s 27 to 8 win over Florida at a neutral site was by 19 against an expected 12.44. The error was 6.559, and 2/16 of that is a gain of 0.820. Ole Miss won 45 to 15 at home over Auburn, a margin of 30 that counted as 28, against an expected 10.60, and gained 2.175, which moved it from 7th to 4th. Texas won 31 to 3 at home over Mississippi State, a margin of 28 against an expected 14.63, gained 1.672, and moved from 8th to 6th. Notre Dame’s win over Navy was smaller than expected and cost it 0.241, so it moved from 6th to 7th. Miami won 38 to 35 at North Carolina against an expected 14.71, lost 1.464, and fell from 5th to 8th. Indiana beat Minnesota 23 to 16 at home against an expected 17.85, lost 1.277, and moved from 9th to 10th. Tennessee was idle and moved from 10th to 9th. In all, 26 teams were idle in week 9, and 3 of them were in the top 10: LSU, Alabama and Tennessee.
Next week
22 of the 138 teams moved 10 or more spots in our rating this week, and 2 moved 20 or more: Jacksonville State up 20 spots and UCF down 22. Last week’s edition said the week 9 schedule had no game between two teams in our top 20. Week 10 has six: Alabama (3rd) at LSU (2nd), Georgia (1st) at Ole Miss (4th), Texas (6th) at Missouri (12th), Texas A&M (20th) at South Carolina (13th), Kentucky (19th) at Tennessee (9th), and Miami (8th) at Notre Dame (7th). The full board, in-season through week 9, is on our college football power ratings page.