While the Pac-12 lost a lot of star power at running back from 2012 -- Kenjon Barner, Johnathan Franklin, Stepfan Taylor and John White -- it also welcomes back a strong core of ball carriers.

Four RBs are back who gained at least 900 yards, and that includes the nation's leading rusher in Arizona's Ka'Deem Carey.

Still, there is uncertainty at the position for a number of schools.

Evaluations aren't easy here. A number of teams have an A-list leading rusher back but uncertain depth. Others have plenty of experience returning but no proven A-lister. So stars and depth matter here.

So how does it stack up?

GREAT SHAPE

Arizona: Carey rushed for nearly 2,000 yards last year and could eclipse that mark this fall. He also scored 23 TDs and averaged 6.4 yards per carry. The depth behind him is solid.

Arizona State: Marion Grice and D.J. Foster, as noted by the Arizona State sports information office, produced 2,130 combined yards in 2012 (1,172 rushing, 958 receiving) and 25 touchdowns. Grice averaged 6.6 yards per carry, Foster 4.8. Both are good receivers. They are one of the best combos in the nation, if not the best.

Washington: Bishop Sankey ranked fourth in the Pac-12 in 2012 with 110.7 yards rushing per game. He averaged 5.0 yards per carry and scored 16 TDs. There's good depth behind him, particularly if Jesse Callier is back to form after a knee injury.

Oregon: While running back is one of the Ducks questions, that question is more about how they will do things rather than whether or not they will be good. If De'Anthony Thomas is the No. 1 running back and gets 15 to 20 carries a game (and, knock on wood, stays healthy), he'll be a money guy. Byron Marshall is capable and incoming freshman Thomas Tyner is highly touted.

USC: Silas Redd is back after rushing for 905 yards, but he'll have to fight off some youngsters who want the ball, namely freshman Justin Davis, who was impressive in spring practices. There's also D.J. Morgan, and don't forget about Tre Madden, who offers a power option after sitting out last year with a knee injury.

Oregon State: Storm Woods and Terron Ward combined for 1,747 yards (1,355 rushing, 392 receiving) and 19 touchdowns in 2012. Woods rushed for 940 yards and 13 TDs, despite being banged up much of the year. Ward averaged 6.1 yards per carry. These guys won't wow you but they are a strong pair.

GOOD SHAPE

Stanford: The Cardinal is replacing Taylor's conference-high 322 carries, so even if the prospects are strong, there's some question of if it will be one or two guys or a committee. The return of Tyler Gaffney from pro baseball is big. He had 449 yards and seven TDs in 2011 before taking a year off. There's also Anthony Wilkerson, the most likely starter, Ricky Seale, Remound Wright and Barry Sanders. The Cardinal does get a boost from the return of fullback Ryan Hewitt.

California: The Bears might have an outstanding combination here with Brendan Bigelow and Daniel Lasco. Both have flashed potential, particularly Bigelow, who rushed for 431 yards and averaged 9.8 yards per carry -- yeah, 9.8 yards -- in 2012. But they are not a sure-thing. Bigelow has trouble staying healthy, and Lasco had just six carries last year, though one went for 77 yards.

Colorado: Everybody of note is back, led by 235-pound sophomore Christian Powell, who rushed for 691 yards and seven TDs, averaging a solid 4.4 yards per carry. There's also Tony Jones and Donta Abron to compliment Powell's power with some breakaway ability. Of the Buffs worries, running back is way down the list.

WE'LL SEE

UCLA: Replacing Franklin won't be easy, and it's likely this one will be by-committee, because no single player looks like a go-to guy. Jordon James, Paul Perkins, Malcolm Jones, Steven Manfro and Damien Thigpen, who is coming back from a knee injury, are in the mix. James was the top backup last year, while Perkins is the intriguing redshirt freshman. Thigpen, if healthy, is a slash type guy who isn't a pure running back.

Utah: White, the first Ute to rush for more than 1,000 yards in consecutive seasons, is gone. Kelvin York, White's backup, now gets his shot after rushing for 273 yards last year. He, however, has some injury worries. Behind him, there's Lucky Radley, James Poole and 243-pound Karl Williams. It's also possible JC transfer Devontae Booker will get into the mix. The Utes should be OK here but the pecking order isn't yet clear.

Washington State: Does this position even apply for the Cougars? Last year, they ranked last in the nation in rushing with 29 yards per game and 1.38 yards per carry. Teondray Caldwell is the leading returning rusher with 269 yards. There's also Leon Brooks and Marcus Mason. The issue here isn't the running backs. It's the run blocking, which was pitiful last year.