Texas is back at No. 1 in the Associated Press college football top 25 and Ohio State is back at No. 2 after a weekend of upsets caused major upsets that dropped previously-highest-ranked Alabama to seventh.

The Crimson Tide was one of five teams ranked in the top 11 on Saturday that lost. Alabama's loss to Vanderbilt was the centerpiece, as the Tide lost to the Commodores for the first time in 40 years, marking just the second loss by a No. 1 team to an unranked team in college football in the last 16 seasons.

Texas, which escaped the chaos that descended on the SEC by elimination, received 52 first-place votes and moved back to No. 1 after being bumped to No. 2 last week when the Crimson Tide beat Georgia. No. 2 Ohio State received nine first-place votes, followed by Big Ten rivals Oregon at No. 3 and Penn State at No. 4. The Buckeyes and Ducks meet in a top-three matchup next Saturday night in Eugene each other.

Georgia maintained its spot at No. 5 and Miami, which became the fifth ranked team to narrowly avoid a loss to an unranked team when it rallied from a 25-point deficit to beat Cal, moved up two spots to No. 6 .

Behind Alabama is No. 8 Tennessee, the other top-five SEC team upset on the road Saturday. The Vols fell to Arkansas 19-14. No. 9 Ole Miss and Clemson round out the top 10.

No. 22 Pitt and No. 25 SMU rose in the rankings for the first time this season, and previous No. 11 USC, No. 22 Louisville and No. 25 UNLV were eliminated (26 teams were ranked last week due to a tie ).

Others receiving votes: USC 98, Nebraska 51, Navy 43, Army 33, Vanderbilt 26, Arkansas 17, Washington State 8, Iowa 8, Texas Tech 7, Syracuse 6, Washington 4, Louisville 4, Colorado 3, Kentucky 1

More change at #1

Turnover at No. 1 is already higher than anything college football has seen in a long time. The last time three different teams held the No. 1 seed in Week 6 was 2008, when Georgia was the top team in the preseason before immediately dropping it to USC — even though the Bulldogs won their opener — and then Oklahoma after the Trojans The top seed was upset by Oregon State and unranked Jacquizz Rodgers in a famous game Thursday night in Corvallis.

In total, the No. 1 has already changed hands three times between three teams this season. The last time the No. 1 ranking changed hands three times in the first six weeks of the season was in 1984, when it moved from preseason No. 1 Auburn to Miami to Nebraska to Texas in Week 5, according to College Poll Archives. – Russo

How surprises changed the top 25

Typically, there's a Saturday sometime in early October when the results cause voters to hit the reset button on the AP poll and really start abandoning any preseason notions. This was one of those weekends.

One of the most notable moves was Clemson not only recovering from an opening loss to Georgia, but entering the top 10 at No. 10 for the first time this season.

No. 11 Iowa State also moved up five spots to match its season-high ranking. No. 18 Indiana did the same. There is a three-way tie at 18 between the Hoosiers, Kansas State and Oklahoma.

No. 15 Texas A&M opened up a 10-spot lead after beating Missouri, while the Tigers slipped 12 spots to No. 21 and Michigan's second loss of the season dropped the Wolverines 14 spots to No. 24. – Russo

How wild was week 6?

• Seven of the 18 ranked teams lost, starting with UNLV's overtime loss to Syracuse late Friday night.
• Six ranked teams lost to unranked opponents.
• Saturday was the first day four of the top 11 teams lost to unranked opponents since five on November 12, 2016.
• Saturday was the first day that two of the top four teams lost to unranked opponents since November 12, 2016.
• Vanderbilt's win over Alabama was its first against an AP top-five team in 61 tries.
• Arkansas' win over Tennessee was its first against an AP Top 5 team since 2007 against No. 1 LSU, which still won the BCS title.
• Texas A&M's 41-10 win over No. 9 Missouri was its most against a top-10 opponent, surpassing its 52-28 win over No. 9 South Carolina in 2014.

And the week was about to get even more chaotic as Miami needed a big comeback to beat Cal. – Brown

Go deeper

Where Vandy vs. Alabama ranks as one of the No. 1 upset wins of all time

How Matt voted

This was one of the most difficult ballots I have completed in eight seasons as a voter. With Texas, Ohio State and Oregon, the top three were easy to reach. Thereafter …

How far should Alabama fall? There is no good answer. Alabama got arguably its best win among the top teams when it defeated Georgia last week. Alabama also has one of its biggest losses, against Vanderbilt. Since the Bulldogs and Crimson Tide had identical records, I stuck with the head-to-head matchup and kept Alabama ahead of Georgia (and Georgia ahead of Clemson). Alabama dropping to No. 6 on my ballot doesn't feel like a penalty, but I had a hard time putting anyone else over the top.

I have Boise State in my top 10. Why not? The Broncos' only loss was by three against No. 3 Oregon. They have a leading Heisman Trophy candidate in Ashton Jeanty, who has already rushed for 1,000 yards, and they also earned a comfortable win over Washington State, 4-1. In the race for open spots, they deserve it as much as anyone else, with barely any gap between the back of the top 10 and the back of the poll.

Texas A&M is my biggest climber. I didn't have the Aggies ranked, but had them bumped to No. 14 — one spot behind Notre Dame — after their dominant win over Missouri. Their win against Arkansas also looks better after the Razorbacks upset Tennessee.

Tennessee remains on my ballot; Michigan, USC and Missouri are out. I demoted the Vols from No. 3 to No. 15 after their narrow loss to Arkansas. They still have the win over Oklahoma, but the credit for knocking out what turned out to be a bad NC State team is waning. I saw no reason to keep Missouri in the rankings despite having it at No. 9, as the Tigers beat Boston College and Vandy by a combined nine points before losing to Texas A&M by 31 points. And Michigan and USC, who played a dramatic game a few weeks ago, both had two losses.

The only two-loss team I ranked? Vanderbilt. Hey, with so much excitement, you have to give the Commodores credit for beating the No. 1 seed. I have them in 22nd place.

Welcome to my choice, Army (24) and Navy (23). The Black Knights and Midshipmen are a combined 10-0 – and they win dominantly. – Brown

Will the chaos continue?

The start of this season brings back memories of 2007.

That 2007 season set the modern standard for equality and unusualness in college football. More recently, super teams have dominated the top of the rankings, rarely losing to other than other highly ranked teams.

There have already been eight instances this season where top 10 teams have lost to unranked teams. As ESPN's Bill Connelly pointed out on social media Sunday morning, nine top-10 teams lost to unranked teams in six weeks of the 2007 season. This season, four teams held first place: USC, LSU, Ohio State and Missouri (for one week), and it changed hands six times. LSU became the only national champion with two losses. With the expanded playoffs and bigger power conferences than ever before, we could be heading toward that again.

Where this season probably doesn't match 2007 is the diversity of teams that finished in first place. Here are some of the teams that finished No. 2 this season: California, South Florida, Boston College, Oregon, Kansas and West Virginia.

In this era of superconferences, it's unlikely we'll get anything like that — but keep an eye out for Indiana and Boise State. – Russo

What's next in week 7?

The Big Ten takes center stage in prime time as No. 2 Ohio State hosts No. 3 Oregon in the biggest game of the season so far. The winner will clinch the No. 1 seed, although Texas hosts a matchup with No. 18 Oklahoma to retain that spot before visiting Georgia on Oct. 19.

With USC knocked out of the poll following its loss to Minnesota, its season may be on the line with a visit from No. 4 Penn State. There's also another SEC rankings matchup, with No. 9 Ole Miss facing No. 13 LSU.

Required reading

(Photo: Carly Mackler/Getty Images)