Utah wide receiver Britain Covey celebrates after scoring a touchdown (AP Photo/Ryan Kang)

At the midway turn of the 2015 season, much of the college football landscape has been altered.

Four of the top 10 teams in the Associated Press preseason poll — Auburn, Oregon, USC, Georgia — are no longer in the top 25. Michigan State and Alabama have fallen out of the top five, and 14 teams remain unbeaten. Also, LSU running back Leonard Fournette has run, stiff-armed and hurdled his way to the front of the Heisman Trophy race.

Three teams, though, have captivated their respective fans with overachieving first-half performances.

[This weekend’s college football TV schedule, preview]

Utah (6-0, 3-0 Pac-12)

Neither the coaches nor the AP had Utah ranked in the preseason polls and none of ESPN’s 28 experts picked the Utes to win the Pac-12. Moreover, the conference’s media poll predicted they would finish fifth in the Pac-12 South Division.

Fast forward to today: The No. 7 Utes are the lone undefeated team in the conference, with a two-game lead in the South Division and wins over Michigan, Oregon (on the road, in historic fashion), California and Arizona State. Utah has received a regular season first-place vote in the AP poll for the first time in program history, and one Sports Illustrated writer even has them projected to win the national championship.

I’ve coached about 280 games here and this is the best group of guys to be around,” Coach Kyle Whittingham said after Saturday’s 34-18 win over the Sun Devils. “I’ve been coaching a lot of years here and coached a lot of games and I can’t remember when I’ve been more excited about what we’re doing.”

Let’s remember that this program has only six seasons with at least 10 wins in its history. Alabama, for context, came into 2015 looking for its seventh straight season with at least 10 wins. Next, consider that after handing Oregon its worst defeat in more than 30 years, the Utes reloaded the next week and intercepted Cal quarterback Jared Goff — one of, if not the best NFL quarterback prospect in the country — five times.

Utah is sound offensively, completing nearly 70 percent of its passes, churning out first downs in volume and rarely accruing penalties. But the team’s defense under coordinator John Pease has been ravenous. The Utes lead the conference and rank second nationally in interceptions (13), and also lead the conference in rushing defense.

Don’t be surprised if they’re one of the four teams that end up in the College Football Playoff.

Memphis (6-0, 2-0 AAC)

Memphis wasn’t picked to win the American Athletic Conference and was left out of the preseason polls.

But last weekend’s 37-24 victory over then-No. 13 Ole Miss marked the 13th consecutive win for the program, and the Tigers have as much momentum as any team in the country.

We’ve accomplished some great things,” Coach Justin Fuente said, “but those are gone and we have to continue to move forward.”

Under Fuente and offensive coordinator Dan Werner, the Memphis offense is averaging a staggering 532.8 yards per game.

The Tigers rank eighth in the country in Football Outsiders’ Offensive S&P+ metric, ahead of the high-powered offenses at Ohio State, Oklahoma, and Clemson.

With a stronger record thus far than No. 21 Houston and No. 22 Temple — the AAC’s other unbeaten teams — and potentially three wins over ranked opponents come season’s end, the No. 18 Tigers are in prime shape for a second-half run at the College Football Playoff.

Iowa (7-0, 3-0 Big 10)

While much of the offseason discourse surrounding Coach Kirk Ferentz tilted toward the negative, the No. 12 Hawkeyes are off to the program’s best start since 2009.

We haven’t split atoms or anything like that,” Ferentz said recently. “We’re just trying to do everything a little bit better. I know it sounds simplistic, but that’s really what it gets down to.”

While Ferentz is indeed correct, the Hawkeyes are exceeding any and all expectations this year. The Big Ten Network’s Tom Dienhart predicted the Hawkeyes would finish eighth in the conference; ESPN’s Brian Bennett said they’d finish ninth. They didn’t receive votes in the preseason in either the AP or the coaches’ poll.

Which is to say that nobody predicted they’d make it this far.

Defensive coordinator Phil Parker’s outfit boasts a top 10 scoring defense, which has only allowed opponents to reach the 20-point mark twice and ranks 14th in efficiency.

Much of the credit should be pointed to Parker’s rushing defense, which ranks allows just 2.46 yards per carry  and ranks sixth in the country in Football Outsiders’ S&P rushing metric, which adjusts performance based on the opponent and is engineered around efficiency, explosiveness, field position, finishing drives and turnovers.

With games left against Maryland, Indiana, Minnesota, Purdue and Nebraska, the Hawkeyes are the likely team to represent the Big Ten West in the conference title game. A win there would vault them into the College Football Playoff picture — far from where the preseason projections pegged them to be.

Josh Planos has been published at the Wall Street Journal, the Atlantic, the Guardian, the Pacific Standard and VICE, among other publications. He has been heard on CBS Sports Radio, Fox Sports Radio and ESPN Radio. Planos is currently a Digital Editor at KETV NewsWatch 7 and a freelance writer.