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Teams with 1st loss Week 5:
Navy
California
Virginia
Kansas State
UAB

Teams with 2nd loss Week 5:
Virginia Tech
San Jose State
Nebraska
Texas Tech
Mississippi State
Southern California
Washington State
Indiana
Boston College
Iowa State
Coastal Carolina
Marshall
New Mexico
Troy
North Carolina State
Nevada

Teams with 1st win Week 5:
Vanderbilt
Massachusetts

Maximum number of Undefeated Teams at the End of the Regular Season:
7: All conference champs except the champs of the MAC, PAC-12, and Conference USA. This is down two from last week with the final unbeatens in the PAC-12 (Cal) and Conference USA (UAB) losing.

Teams with 1st loss:
Week 0 and 1: 35.38% (46 of 130)
Week 2: 38.01% (32 of 84)
Week 3: 32.69% (17 of 52)
Week 4: 34.29% (12 of 35)
Week 5: 21.74% (5 of 23)

Week 5 Thoughts:
-Let's start in the winless column as we lost 2 of our last 5 teams who had yet to win. Vanderbilt's win removes the final team from a power 5 conference. UMass won the battle of winless teams. There will be no more of those this season.

-Biggest news of the week was probably Clemson's close game vs. North Carolina. At the end of the day, a loss probably wouldn't have killed them given the the talent on the team, but given a softer top of the ACC this year (outside of Clemson of course), it's best for them not to have this be regular (won't matter if they win out, but if lose one and struggle and several others, the schedule might matter).

-With Cal's loss, the PAC-12 is the first power 5 conference to lose its last undefeated team. They need to hope for one of the 1-loss teams to go the distance and hope for a lot of help. Oregon is the best bet. Right now, the PAC-12 reminds me of the ACC of about a decade ago. It had a lot of strong, but no dominant/elite teams. This makes every week exciting, but is a bad combination for national title runs as teams tend to beat up on each other and knock each other out.

-In the race for the Group of 5 NY6 bowl spot, Conference USA's chances took a big hit with UAB's first loss. My view is Confernece USA and the MAC only really stand a chance now with a major upset late in the season by a 1-loss team over a highly ranked team (although I'm not right now looking into the schedules to see who would have the chance of that). Appalachian State of the Sun Belt held onto undefeated status this week. They would definitely need the 3 undefeateds from the American and Mountain West to lose and might need 2 loss champs from those conferences, but are still alive as long as they keep winning. Our biggest game of week in this race though last week was probably Memphis beating Navy (our only game between undefeated teams at all last week). Memphis and SMU are now the last 2 undefeated teams in the American.

Week 6 Thoughts:
We have 1 game between undefeated teams this week.

Undefeated Auburn @ Undefeated Florida: Florida despite being ranked #10 has not gotten the attention the other top SEC teams have. Win this and they will. They'll also be in a 2 team team race with Georgia for the SEC East. Auburn has a tougher road still, but that makes winning it even more imperative. It's likely the SEC West representative to Atlanta will have no more than 1 loss. Lose this and you probably have to win out the rest of the way and that includes games with Georgia, LSU, and Alabama.

1-loss UCF @ 1-loss Cincinnati (Friday): This is a big game in the American east. UCF is only a slight favorite here and if Cincinnati wins, they will probably get into the top 25 and be the favorite to win the east. Regardless the loser here would have a very uphill battle of getting into a NY6 bowl even if they recovered in conference.

Undefeated Iowa @ 1-loss Michigan: Very big and telling game between the 2 schools. If Iowa wins and stays unbeaten, it becomes a very clear 2 way race between them and Wisconsin for the Big Ten West. Michigan needs this game badly though. Their overall schedule is incredibly tough this year and this far in, fans are getting very restless with Jim Harbaugh. A loss here for Michigan with Penn State, Michigan State, Notre Dame, and Ohio State still to go is not a recipe for success.

Undefeated Baylor @ 1-loss Kansas State: The Bears are still undefeated. This will be an interesting road test.

1-loss Arizona @ 1-loss Colorado: Winner will sit atop the PAC-12 south for at least now.

1-loss Michigan State @ undefeated Ohio State: Buckeyes have looked very good so far. Michigan State has given them plenty of fits in past though.

-Akron is off, but our other 2 winless teams are playing. New Mexico State is the more likely one to win playing at home vs. Liberty as 5 point underdogs. Rice plays at 3-1 UAB as an 8.5 point underdog.

Remaining Undefeated Teams: ACC: 2, American Athletic: 2, Big 12: 2, Big Ten: 5, Conference USA: 0, Mountain West: 1, PAC-12: 0, SEC: 5, Sun Belt: 1, total: 18
Clemson
Wake Forest
Baylor
Oklahoma
Iowa
Minnesota
Ohio State
Penn State
Wisconsin
Memphis
Southern Methodist
Florida
Georgia
Alabama
Auburn
Louisiana State
Boise State
Appalachian State

1-loss Teams: ACC: 2, American: 5, Big 12: 5, Big Ten: 2, Conference USA: 2, MAC: 2, Mountain West: 5, PAC-12: 7, SEC: 1, Sun Belt: 1, independents: 2, total: 34
Duke
Central Florida
Cincinnati
Temple
Tulane
West Virginia
Texas Christian
Texas
Oklahoma State
Michigan State
Michigan
Louisiana Tech
Eastern Michigan
Toledo
Wyoming
Utah State
Hawaii
Air Force
San Diego State
Oregon
Washington
Arizona
Colorado
Utah
Arizona State
Missouri
Louisiana-Lafayette
Army
Notre Dame
Navy
California
Virginia
Kansas State
UAB

 Remaining Winless Teams: Conference USA: 1, MAC: 1, SEC: 0, independents: 1, total: 3
Rice
Akron
New Mexico State

Thank you for posting, I always enjoy following this.  

Undefeated teams in the rankings (using AP here, rankings after the top-25 are using the place among ORV):

• #1 Bama
• #2 Clemson
• #3 Georgia
• #4 Ohio State
• #5 LSU
• #6 Oklahoma
• #7 Auburn
• #8 Wisconsin
• #10 Florida
• #12 Penn State
• #14 Iowa
• #16 Boise State
• #22 Wake Forest
• #24 SMU
• #28 Memphis
• #29 Appalachian State
• #32 Baylor
• #34 Minnesota

Thoughts on the undefeated teams that remain unranked.  This list is down to just four teams and it is going to get shorter really soon:

• #28 Memphis:  The Tigers' win over Navy got them close to the top-25 and if they win their next two (ULM and Temple) they'll be ranked so in no more than two weeks, they'll be off this list one way or the other.  
• #29 Appalachian State:  The Mountaineers don't have any ranked teams on the slate this year but they are already close to the top-25 so it is a safe bet that they'll also be off this list one way or the other within two or three weeks.  
• #32 Baylor:  The Bears are a P5 team and they play Kansas State this Saturday.  Kansas State is 3-1 with the lone loss being at #21 OkSU so if the Bears win this weekend they'll probably appear in the next top-25.  
• #34 Minnesota is the most interesting of the group.  The Gophers are 4-0 but they won the four games by a combined 20 points and it isn't like they played murderers row either.  They could potentially stay on this list until November.  They play Illinois this weekend and Nebraska next weekend both at home.  Winning those two might get them ranked but beating the Illini at home isn't going to impress anyone and even beating Nebraska wouldn't be all that impressive if they barely win.  After that they travel to Rutgers on 10/19 which is another game where a win will not impress anyone.  Then they come home to face Maryland on 10/26 before a week off.  It is doubtful, but the Gophers could get to 8-0 and still be unranked.  

Thoughts on the P5 undefeated teams (excluding Baylor and Minnesota which I already covered):
The thing to watch here is the clumping of P5 undefeated teams at the top.  That will accelerate rapidly this week mostly due to UF/Auburn and IA/M.  If either Iowa or Florida win they will join the block of P5 undefeated teams at the top of the rankings.  

Penn State is #12, behind two teams with losses (#11 Texas and #9 ND) and they host Purdue this week in a game that will not help them move up much even if they win.  After that they travel to Iowa City then host Michigan.  Obviously if they are still undefeated after playing the Hawkeyes and Wolverines they will be in the block of undefeated P5 teams at the top of the rankings.  

Wake Forest will have to wait a bit longer.  Their next four opponents each have two losses but after that comes a two-game stand against undefeated and #2 Clemson followed by 3-1 Dook.  Obviously if the Demon Deacons are still undefeated after playing Clemson they'll be in the block of undefeated P5 teams at the top of the rankings but probably not unless and until that happens.  

For more detail on the race for the G5's NYD Bowl spot, here are the G5 teams that are ranked or receiving votes:

• #16 Boise State 4-0, MWC
• #18 UCF 4-1, AAC
• #24 SMU 5-0, AAC
• #28 Memphis 4-0, AAC
• #29 ApSt 4-0, Sunbelt
• #30 Army 3-1, Independent
• #37 Tulane 3-1, AAC

It seems to me that barring a series of major upsets, this is between Boise State and the AAC Champion.  ApSt would likely need at least for both of those teams to have a loss and everybody else is behind that in the pecking order.  

Of the undefeateds, how many play other undefeateds later in the year?

Florida plays Auburn/LSU/UGA, so they hit three for example.  Ohio State plays PSU and Wisconsin.

Maybe that matrix is still too complex to be of use.

Here is most of it.  I used to do the "maximum number of undefeated teams" thing but Ohio1317 took that over.  It is really pretty simple now:

• Two ACC teams will pare down to no more than one as of the Clemson/Wake game on 11/16.
• Two AAC teams will pare down to no more than one as of the SMU/Memphis game on 11/2.  
• Two B12 teams will pare down to no more than one as of the OU/Baylor game on 11/16.  
• Five B1G teams will pare down to no more than two prior to the B1GCG* and no more than one after the B1GCG.  
• Five SEC teams will pare down to no more than two prior to the SECCG* and no more than one after the SECCG.  

In the B1G:  The five undefeated teams are:

• Ohio State:  Plays PSU and UW before B1GCG
• Wisconsin:  Plays tOSU, IA, and MN before B1GCG
• Penn State:  Plays tOSU, IA, and MN before B1GCG
• Iowa:  Plays PSU, UW, and MN before B1GCG
• Minnesota:  Plays PSU, UW, and IA before B1GCG

Thus, the only mathematically possible B1GCG match-ups of undefeated teams are:

• tOSU v IA
• tOSU v MN
• UW v PSU

In the SEC:  The five undefeated teams are:

• Bama:  Plays Aub and LSU before SECCG
• Auburn:  Plays Bama, LSU, UF, and UGA before SECCG
• LSU:  Plays UF, Bama, and Aub before SECCG
• Florida:  Plays UGA, Aub, and LSU before SECCG
• Georgia:  Plays UF and Aub before SECCG

Thus, the only mathematically possible SECCG match-ups of undefeated teams are:

• Bama v UGA
• Bama v UF
• LSU v UGA

I'd like to see Cincinnati get called up.  Finkle might get called up first.

Always enjoy the commentary Medina.  Thank you.  Also, sorry took on maximum number.  Not really sure why or when did.  I post this one other place and guess I just added it a year. 

Given random upsets and expected results, I would only expect a few more games between undefeateds in regular season.  I think 1 or 2 would definitely be most likely in the Big Ten (and think betting odds would actually favor only one) and think SEC would only be marginally higher in odds after this week (once Florida/Auburn done).  Its very doubtful the ACC or Big 12 games take place between undefeateds.  Memphis/SMU odds are against too (although not to same degree).  All in all, I am guessing 4 games between undefeated teams before bowl season after this week.

Always enjoy the commentary Medina.  Thank you.  Also, sorry took on maximum number.  Not really sure why or when did.  I post this one other place and guess I just added it a year. 

Given random upsets and expected results, I would only expect a few more games between undefeateds in regular season.  I think 1 or 2 would definitely be most likely in the Big Ten (and think betting odds would actually favor only one) and think SEC would only be marginally higher in odds after this week (once Florida/Auburn done).  Its very doubtful the ACC or Big 12 games take place between undefeateds.  Memphis/SMU odds are against too (although not to same degree).  All in all, I am guessing 4 games between undefeated teams before bowl season after this week.

Please don't be sorry.  I like having it as part of the initial post.  

It is a little bit less important than it was back in the BCS era because back then being undefeated was a bigger deal.  

I agree with your guess of about four more games between undefeated teams.