Week 4 is in the books as we look back at surprising performances and key storylines from this weekend's games.

No. 1 Texas remained on top in the rankings with backup quarterback Arch Manning getting his first career start. As injuries affect multiple top-ranked teams this season, it shows just how important roster depth is to be a true contender for the national title.

Colorado's overtime victory over Baylor showcased yet another reason why college football fans should be watching Travis Hunter this season. After recording 130 receiving yards and forcing a game-clinching fumble for the Buffaloes, Hunter continues to show his elite playmaking skills each week.

Our college football experts break down key takeaways from Week 4 performances.

True CFP contenders need depth to survive the season

It's not even October yet and multiple College Football Playoff contenders -- including No. 1-ranked Texas and No. 10 Utah -- have started their second-string quarterbacks because of injuries. In its historic Week 3 win at Purdue, Notre Dame lost starting linemen Ashton Craig and Jordan Botelho to season-ending injuries. Michigan tight end Colston Loveland -- the Wolverines' top pass catcher -- missed Saturday's win against USC with an undisclosed injury.

These teams -- and any others with hopes of winning the national championship in the era of the 12-team playoff -- have to be built to last through Jan. 20.

As inclusive as the new 12-team format is, the true contenders for the national title are the ones that have the depth to overcome injuries at critical positions, and that's a small pool of candidates: Alabama, Georgia, Ohio State and Texas.

The list isn't too much longer. It's the wealthiest programs with the resources to lure in enough offensive and defensive linemen who can rotate through the national title game on Jan. 20. The teams whose No. 2 QB is as good as QB1. It's now a game of attrition as much as it is a game of inches. -- Heather Dinich

Heupel makes his return to Norman

A funny thing happened on the way to what looked to be another Tennessee offensive fireworks show in its 25-15 road win Saturday at Oklahoma. Coach Josh Heupel and the Vols actually went conservative in the second half after building a 22-3 lead.

And no, he wasn't feeling sorry for his alma mater. In fact, far from it. He didn't break away from his go-for-it offensive identity just because he had a big lead. Rather, Heupel showed that he has continued to grow as a head coach. He's not just an offensive guru. He understands all the working parts of a football team and how they fit together depending on the circumstances.

So, while some fans lamented that Heupel took his foot off the gas too early, the truth is he coached efficiently and wisely. He didn't allow his pride to get in the way by trying to pile on points in what was clearly an emotional return to the place where he was fired 10 years ago as offensive coordinator. Most importantly, Heupel wasn't going to take unnecessary chances with two backup offensive tackles protecting quarterback Nico Iamaleava most of the night against a really good Oklahoma defense.

Here's what else Heupel knows: He has a better defense right now than an offense, and when the situation warrants, he's going to play to a smothering defense that's a prerequisite if you're going to win a championship. Tim Banks' unit is first nationally in total defense and second in rushing defense and third-down defense.

Some of the best news for the Vols, who have their toughest two tests of the season coming up against Alabama (Oct. 19) and Georgia (Nov. 16), is that they're only going to get better on offense with a quarterback who can make every throw and is becoming more seasoned each week in his first year as a starter.

Tennessee is anything but a finished product and still has a lot to prove, but it has the most complete team Heupel has had in Knoxville and is playing with an edge.

And it starts with the Vols' coach, who's as content winning ugly as he is pretty.

"Our best football is still out there," Heupel said. -- Chris Low

No one is doing it like Travis Hunter

As we witness Shohei Ohtani stitch together one of the most ridiculous seasons in MLB history (without even pitching this season), it's important to acknowledge -- even if it's week after week -- what Travis Hunter is doing in college football.

On Saturday, he had his fifth straight game of 100 receiving yards or more -- the longest such streak in the sport -- and forced the fumble on defense that clinched the win for the Buffs.

Hunter's uniqueness goes beyond playing both ways -- it's that he's an elite playmaker on both sides of the ball.

In four games this season, he has 427 passing yards and five touchdowns, averaging 12.8 yards per catch. On defense, he is nearly halfway to his solo tackles total (23) from last year, has one interception and that aforementioned forced fumble. There are a lot of things that are off-kilter about the Colorado experience, but Hunter is not one of them.

In some ways, I think back to Ohtani and how he has been able to focus on just being the best hitter (and baserunner) in the world this season. It makes you wonder what Hunter could do if he just played wide receiver or if he played only in the secondary. It would make him easier to compare to other players, easier to quantify his impact and perhaps easier to appreciate.

While the "what if" is a tantalizing thought experiment, I prefer to relish that the phenomenon of Hunter is that he has no peers. -- Paolo Uggetti

Problems on the Plains

We've spent much of the past year fretting over coach Billy Napier's status on the hot seat for his inability to right the ship at Florida in a timely enough fashion, but perhaps we've been focused on the wrong SEC coach.

Napier's Gators went into cowbell country Saturday and delivered an emphatic win over Mississippi State with nearly flawless QB play from Graham Mertz and DJ Lagway, who combined to have just two incompletions.

Meanwhile, Auburn lost at home for the fourth time in its past six games -- 24-14 to Arkansas -- behind yet another miserable day of quarterbacking from Hank Brown and Payton Thorne.

A quick accounting of how bad things are:

• Auburn is 0-2 against Power 4 opponents this year

• Auburn is 6-19 in its past 25 games against power conference foes

• Auburn has not beaten a Power 5 team that finished the year with a winning record since Halloween weekend of 2021

For head coach Hugh Freeze, the numbers are just as damning. He finished his stay at Liberty by dropping four straight, including an embarrassing home loss to New Mexico State. He began his Auburn career by dropping 10 of 16 games vs. FBS competition, including an embarrassing home loss to New Mexico State.

While Napier's flagging Florida program at least has a solid veteran QB and a dynamic freshman to build around, Auburn's numbers at the position under Freeze since 2023 are a train wreck: 51.5 Total QBR, completing 59%, 5.6 yards per dropback, 29 touchdowns and 19 turnovers. Thorne was benched after throwing four picks in a loss to Cal two weeks ago, only for Brown to be benched Saturday after throwing three against Arkansas.

Making matters worse, one of Freeze's former quarterbacks, Bo Wallace, took to X in the waning moments of Auburn's latest loss to gleefully celebrate Freeze's failures, suggesting the coach had abandoned him as soon as he could no longer help Freeze win games.

Since the start of last season, Florida has one fewer win but a better record in conference play, is averaging more points per game, and has had markedly better QB play (65.7 Total QBR). So why is Napier on the hottest seat of them all?

Auburn took a major risk in hiring Freeze, a coach whose on-field résumé had been exceptional, but whose off-field reputation was often troubling. It was a calculated gamble to try to right the ship after years of shaky coaching. It's hard to see how the gamble could pay off at the moment, and with its next three games coming against ranked SEC teams, it's likely to get worse before it gets any better. -- David Hale

Surprise! Look who is undefeated in the ACC

Pop quiz, hotshot: Can you name the four undefeated teams left in the ACC? Miami may not be much of a surprise. Louisville, having played in the ACC championship game a year ago, should not be a surprise, either. But how about Pitt and Duke starting the season 4-0? Considering Duke was picked 11th in the preseason media poll and Pitt picked 13th, their hot starts have certainly drawn extra notice.

But there is something all four teams have in common: They each hit on the quarterbacks they chose from the transfer portal. Cam Ward (Washington State) has the prolific Miami offense setting records, while Tyler Shough (Texas Tech) has elevated the Louisville offense into a legitimate threat each week. Maalik Murphy (Texas) helped give new Duke coach Manny Diaz instant credibility with his arrival on campus.

But you could make a legitimate argument the biggest impact portal player could very well be Eli Holstein (Alabama), who won the Pitt starting job in fall camp and has not looked back. His ascendancy has been so unexpected, Pitt brought presumed starter Nate Yarnell to ACC Kickoff back in July. Holstein not only gives the Pitt offense some swag, he and offensive coordinator Kade Bell have been a perfect fit for the tempo offense Bell brought with him from Western Carolina.

Last year, Pitt may have been the poster child for portal quarterbacks who miss -- the Panthers brought in Phil Jurkovec but he never got into a groove, was benched as quarterback and moved to tight end. Coach Pat Narduzzi watched his offense slog through a 3-9 season and thought to himself, "We have to do something different." Enter Bell. The two had never previously worked together, but as soon as Narduzzi -- a defensive coach -- started watching what Bell was doing at Western Carolina he was sold. Pitt has now won more games than all of last season.

All four quarterbacks rank in the top six in touchdown passes thrown in the ACC. Ward, Shough and Holstein rank in the top five in quarterback efficiency. Football is obviously a complex sport, but when the quarterback is playing the way these four are, success can be boiled down in a simple way. Top-tier QB play = success. -- Andrea Adelson

Wolverines find their offense

Michigan had sputtered offensively through its first three games, especially in a loss to Texas in Week 2. But in a come-from-behind win over USC, the defending national champions finally found an offensive identity. Led by senior running back Kalel Mullings, the Wolverines leaned all the way into the running game and pounded the Trojans on the ground.

The Wolverines passed for only 32 yards, their fewest in a game since 1987, according to ESPN Research. But they ran for 290, including 79 on the game-winning drive. Mullings finished with a career-high 159 yards, getting all eight carries on the final possession.

Though he only completed seven passes, new starting quarterback Alex Orji gave Michigan a boost, with 43 rushing yards. The Wolverines now rank last among Power 4 teams in passing. But if they can keep running the way they did against USC, they could reemerge in the playoff conversation. -- Jake Trotter

Group of 5 CFP race adds more twists

The best part of an expanded College Football Playoff is that more teams -- and leagues -- will have something to play for down the stretch. We know that a Group of 5 team will be in the 12-team field, but who gets the golden ticket? Week 4 provided some plot twists as three teams that had previously recorded Power 4 wins -- Northern Illinois, Toledo and Memphis -- all lost. NIU's overtime home defeat to Buffalo likely will sting the most as the Huskies have by far the most impressive nonleague victory, over then-No. 5 Notre Dame on Sept. 7.

Most attention justifiably is on UNLV, which already has wins against two Big 12 teams (Houston and Kansas are a combined 2-6) and gets Syracuse on a Friday night in Las Vegas, following a key home game this week against Fresno State. The Rebels also will host Boise State, which has the most impressive loss among Group of 5 contenders, a 37-34 defeat at Oregon.

Could Liberty, which reached the Fiesta Bowl last year, make it to the CFP despite a schedule once again lacking much substance? James Madison might have entered the mix after putting up 70 points in a win against North Carolina. There's a lot of season left, but the race for the Group of 5's CFP spot is shaping up to be a wild ride. -- Adam Rittenberg