PHOENIX — The SEC has been called the best conference in college football. With seven straight national championships under its belt, it's a tough argument to counter.

PHOENIX — The SEC has been called the best conference in college football. With seven straight national championships under its belt, it's a tough argument to counter.

The one knock about the SEC is that it's top-heavy. While teams like Alabama, LSU, Florida and Georgia always seem to be good, the lower-end teams end up being punching bags for everyone else.

The Pac-12, at least this season, doesn't seem to have that problem.

With national championship contenders at the top and rapidly-improving teams at the bottom, the Pac-12 might be the nation's deepest conference.

"What's happened coaching-wise in our conference and with our competition top to bottom, it's at an all-time high," Oregon State coach Mike Riley said on Tuesday during the Pac-12 coaches teleconference. "It's to the point that there aren't any real surprises as much anymore, just because the competition and the level of play by each team. Each game is going to be very, very interesting."

Through the first five weeks of the season, all but one team in the Pac-12 — California at 1-4 — is .500 or above.

No 2. Oregon (5-0), No. 5 Stanford (5-0) and No. 11 UCLA (4-0) are all undefeated headed into this weekend's games. No. 16 Washington and Oregon State are both 4-1 and Arizona, which plays USC Thursday night, is 3-1.

Arizona State is 3-2, but the Sun Devils have played one of the nation's toughest schedules and recently finished 2-2 on a four-game stretch of games against Wisconsin, Stanford, USC and Notre Dame, all teams that have been ranked this season.

"There is not anybody in the Pac-12 that can't beat anyone," said Arizona State coach Todd Graham, whose team plays an improved Colorado team at home on Saturday. "There is great parity in this league."

That hasn't been the case in recent years, when the Pac-12 has been top-heavy like the SEC, though with a much smaller top: Oregon and USC.

The conference still has two clear favorites, at least in terms of national championship contention, but it's now Stanford with the Ducks leading the pecking order, not the Trojans.

The true strength in the Pac-12 lies behind those two heavyweights.

After struggling the previous two seasons, Oregon State started its resurgence last year, going 9-4 after winning three games in 2011, the biggest turnaround in his school history.

Utah had a rough first season in the Pac-12, going 3-6 in conference to end a nine-year postseason streak, but has been better this season, entering Saturday's game against Stanford 3-2.

Washington State labored in its first season under Mike Leach in 2012, but also has been better, beating USC at the Coliseum for the first time in 13 years while opening the season 4-2.

Colorado also has shown signs up life under new coach Mike MacIntyre, already with more wins than last season at 2-2.

"I've been impressed with the Pac-12," said Leach, in his second season at Washington State after coaching 10 years in the Big 12 with Texas Tech. "There are top-level teams that are big, strong and physical, a lot like there were in the Big 12, and the lower-end teams are really strong. From top to bottom, the Pac-12 is very competitive."

A big difference has been an influx of new coaches.

Jim Harbaugh started Stanford's rise to national prominence and David Shaw, his sharp-minded offensive coordinator, has made the Cardinal BCS title contenders.

Graham overhauled Arizona State's program in his first season, leading the Sun Devils to their first bowl victory since 2005, and appears to have them set up for consistent success.

Rich Rodriguez arrived at Arizona last season after a disappointing three-year run at Michigan and has revitalized the program on and off the field.

Jim Mora has UCLA back on track in a short time frame, Leach is having a similar impact on the Cougars and first-year coaches MacIntyre and Sonny Dykes at California are expected to get their programs back to winning.

"I have seen the conference for a long time and I always thought it was pretty good that way, but I see it at its best now and I see it growing that way, too," said Riley, the conference's longest-tenured coach at 13 seasons. "It's going to be tough."

It already is.